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DOI: 10.1007/s11064-025-04640-3

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What is this?

해당 케이스는 시스템 자동 처리 대상이 아니며, 운영관리팀에서 수기 관리 방식으로 운영할 예정입니다. 운영 절차는 아래와 같습니다.

1)동일 층에서 실거래 변동이 발생한 경우, 매물 노출은 유지합니다. 2)해당 매물은 수기로 별도 관리합니다. 3)별도 관리 기간 동안, 운영관리팀에서 소유주 변경 여부를 주기적으로 확인합니다. 4)동일 호수에서 소유주 변경이 확인된 경우, 소유주 변경에 따른 후속 절차를 진행합니다.

이용 정지 규정에 따라 별도의 ‘1회 경고’ 단계는 적용하지 않습니다. 또한, 누적 횟수 1회는 허위 신고가 누적 3회 발생한 시점을 기준으로 합니다.

English (thorough explanation with images)

1) What deoxyribonucleic means

Deoxyribonucleic is an adjective that describes something related to deoxyribonucleic acid (DNA).

Break the word apart:

• deoxy- → lacking oxygen
• ribose → a five-carbon sugar
• -nucleic → related to the nucleus / nucleic acids

👉 Deoxyribonucleic literally means “nucleic acid containing deoxyribose sugar.”

2) Deoxyribonucleic vs ribonucleic (key contrast)

The term exists mainly to distinguish DNA from RNA.

| Feature | DNA (deoxyribonucleic) | RNA (ribonucleic) | | ------------------- | ----------------------------- | -------------------------- | | Sugar | Deoxyribose | Ribose | | Oxygen at 2′ carbon | H (missing O) | OH | | Stability | More stable | Less stable | | Typical role | Long-term information storage | Short-term information use |

The missing oxygen in deoxyribose makes DNA chemically more stable, which is ideal for storing genetic information long-term.

3) Where “deoxyribonucleic” fits in DNA structure

A deoxyribonucleic acid molecule is built from:

• Deoxyribose sugar
• Phosphate groups
• Nitrogenous bases (A, T, C, G)

Each repeating unit is a DNA nucleotide, and the sugar in every DNA nucleotide is deoxyribose—that’s why DNA is called deoxyribonucleic.

4) Why this term matters biologically

Using deoxyribonucleic highlights:

• DNA’s chemical identity
• DNA’s greater stability
• DNA’s suitability for hereditary storage

If DNA had ribose instead of deoxyribose, it would break down too easily to serve as the genetic archive of life.

5) One-sentence exam definition

Deoxyribonucleic refers to nucleic acids that contain deoxyribose sugar, characteristic of DNA.

中文（配图·深入讲解）

1）deoxyribonucleic（脱氧核糖核的）是什么意思

Deoxyribonucleic 是一个形容词，用来描述 DNA 的化学性质。

拆词理解：

• deoxy-（脱氧） → 少一个氧
• ribose（核糖） → 五碳糖
• nucleic（核酸的） → 与核酸有关

👉 deoxyribonucleic = 含有脱氧核糖的核酸

2）为什么要强调“脱氧”

这是为了区分 DNA 和 RNA：

| 项目 | DNA（脱氧核糖核） | RNA（核糖核） | | ---- | ---------- | -------- | | 糖 | 脱氧核糖 | 核糖 | | 2′ 位 | H | OH | | 稳定性 | 高 | 较低 | | 功能 | 长期储存遗传信息 | 短期传递信息 |

脱氧核糖少一个氧原子，使 DNA 更稳定、不易断裂。

3）deoxyribonucleic 在 DNA 中的作用

DNA 的每个基本单位（核苷酸）都包含：

• 脱氧核糖
• 磷酸
• 含氮碱基（A、T、C、G）

正因为糖是 脱氧核糖，这种核酸才叫 脱氧核糖核酸（DNA）。

4）为什么这是考试关键词

“deoxyribonucleic”强调的是：

• 化学结构差异
• 稳定性优势
• DNA 适合长期遗传保存

这是生命进化中非常关键的一点。

5）一句话考试总结

Deoxyribonucleic 指的是含有脱氧核糖的核酸，是 DNA 的核心化学特征。

如果你愿意，我可以把 ribonucleic vs deoxyribonucleic 做成一张 中英对照结构差异速查表，非常适合 Biology 10 / 11 考前复习。

English (thorough explanation with images)

1) What a karyotype is

A karyotype is an organized picture of all the chromosomes in a cell, arranged in pairs, from largest to smallest, showing their number and structure.

In short:

Karyotype = a chromosome map of a cell

2) How a karyotype is made

To create a karyotype, scientists:

1. Take dividing cells (often blood cells)
2. Stop cell division at metaphase → chromosomes are most condensed and visible
3. Stain and photograph the chromosomes

4. Arrange them into pairs based on:

5. Size

6. Shape
7. Centromere position
8. Banding patterns

3) What information a karyotype shows

A karyotype reveals:

• Total chromosome number
• Sex chromosomes (XX or XY)
• Large chromosomal abnormalities

For humans:

• 46 chromosomes

• 22 pairs of autosomes

• 1 pair of sex chromosomes

4) Autosomes vs sex chromosomes

| Type | Description | | ------------------- | ------------------------------------------- | | Autosomes | Chromosomes 1–22, same in males and females | | Sex chromosomes | X and Y, determine biological sex |

Examples:

• XX → typically female
• XY → typically male

5) Detecting chromosomal disorders (key use)

Karyotypes are commonly used to detect numerical abnormalities, such as:

• Trisomy 21 (Down syndrome) → three copies of chromosome 21
• Turner syndrome → XO
• Klinefelter syndrome → XXY

⚠️ Note: karyotypes detect large-scale changes, not small gene mutations.

6) Karyotype vs genotype (do not confuse)

| Term | What it shows | | ------------- | ----------------------------- | | Karyotype | Chromosome number & structure | | Genotype | Allele combinations of genes |

7) One-sentence exam definition

A karyotype is a visual display of an organism’s complete set of chromosomes, arranged by size and shape.

中文（配图·深入讲解）

1）什么是核型（karyotype）

核型是把一个细胞中的全部染色体拍照后，按照大小、形态和着丝粒位置系统排列得到的图像。

一句话：

核型 = 染色体的“全家福”

2）核型是如何制作的

制作步骤包括：

1）取正在分裂的细胞 2）将细胞固定在分裂中期 3）染色并拍照 4）按以下标准配对和排序：

• 长短
• 形状
• 着丝粒位置
• 条带特征

3）核型能告诉我们什么

核型可以显示：

• 染色体总数
• 性染色体组成
• 明显的染色体异常

人类正常核型：

• 46 条染色体

• 22 对常染色体

• 1 对性染色体

4）常染色体 vs 性染色体

| 类型 | 含义 | | -------- | ----------- | | 常染色体 | 第 1–22 号染色体 | | 性染色体 | X、Y，决定生物性别 |

5）核型的核心用途（考试重点）

核型常用于检测染色体数目异常，例如：

• 21 三体综合征（唐氏综合征）
• 特纳综合征（XO）
• 克氏综合征（XXY）

⚠️ 核型只能看见大尺度异常，看不到基因层面的细小突变。

6）核型 vs 基因型（易混点）

| 概念 | 内容 | | ------- | -------- | | 核型 | 染色体数量和结构 | | 基因型 | 等位基因组合 |

7）一句话考试总结

核型是按大小和形态排列的完整染色体图像，用于分析染色体数目和结构。

如果你愿意，我可以把 chromatin → chromosome → homologous → allele → karyotype 整理成一张 Biology 10/11 中英对照总复习图表，非常适合考前快速回顾。

English (thorough explanation with images)

1) What an allele is (core definition)

An allele is a different version of the same gene.

• A gene controls a trait (e.g., eye color)
• Alleles are the alternative forms of that gene (e.g., brown vs blue)

👉 Same gene, different versions.

2) Where alleles are found

Alleles are located at the same position (locus) on homologous chromosomes:

• One allele comes from the mother
• One allele comes from the father

So, for each gene, most organisms have two alleles.

3) Example (eye color)

At the eye-color gene locus:

• B = brown allele
• b = blue allele

Possible allele combinations:

• BB → brown eyes
• Bb → brown eyes
• bb → blue eyes

4) Genotype vs phenotype

| Term | Meaning | | ------------- | ----------------------------------------- | | Genotype | The allele combination (BB, Bb, bb) | | Phenotype | The observable trait (brown or blue eyes) |

Alleles determine genotype; genotype influences phenotype.

5) Dominant and recessive alleles

• Dominant allele: expressed when present (B)
• Recessive allele: expressed only when two copies are present (b)

In Bb:

• Dominant B masks recessive b

6) Homozygous vs heterozygous

| Term | Alleles | | ---------------- | -------------------------------- | | Homozygous | Two identical alleles (BB or bb) | | Heterozygous | Two different alleles (Bb) |

7) Why alleles matter

Alleles are the source of:

• Genetic variation
• Differences among individuals
• Evolution through natural selection

Small allele differences can lead to big trait differences.

8) One-sentence exam definition

An allele is one of two or more alternative forms of a gene found at the same locus on homologous chromosomes.

中文（配图·深入讲解）

1）什么是等位基因（allele）

等位基因是指同一基因的不同版本。

• 基因决定一种性状
• 等位基因决定该性状的不同表现形式

👉 同一个基因，不同版本。

2）等位基因的位置

等位基因位于同源染色体的相同位置（基因位点，locus）：

• 一个位于 父源染色体
• 一个来自 母源染色体

因此通常一个性状由 两个等位基因控制。

3）举例说明（眼睛颜色）

眼睛颜色基因：

• B = 棕色等位基因
• b = 蓝色等位基因

基因型：

• BB → 棕眼
• Bb → 棕眼
• bb → 蓝眼

4）基因型 vs 表现型

| 名称 | 含义 | | ------- | ---------------- | | 基因型 | 等位基因组合（BB、Bb、bb） | | 表现型 | 实际可观察到的性状 |

5）显性与隐性

• 显性等位基因：只要存在就表现
• 隐性等位基因：必须两个都存在才表现

6）纯合与杂合

| 类型 | 等位基因 | | ------- | -------- | | 纯合子 | 两个相同等位基因 | | 杂合子 | 两个不同等位基因 |

7）等位基因的重要性

等位基因是：

• 个体差异的来源
• 遗传多样性的基础
• 自然选择和进化的原材料

8）一句话考试总结

等位基因是位于同源染色体相同位置的同一基因的不同形式。

如果你愿意，我可以把 gene → allele → genotype → phenotype 整理成一张 Biology 10 高频概念关系图（中英双语），非常适合考前复习。

English (thorough explanation with images)

1) What a chromosome is

A chromosome is a highly condensed structure of DNA and proteins found in the nucleus of eukaryotic cells. Chromosomes carry genes, which contain the instructions for building and maintaining an organism.

Simply: chromosome = tightly packed DNA that holds genes.

2) What chromosomes are made of

Chromosomes consist of:

• DNA (the genetic code)
• Proteins, mainly histones, which help DNA coil and fold

DNA + histones together form chromatin. When chromatin coils up tightly (especially during cell division), it becomes a chromosome.

3) Chromatin vs chromosome (very important)

| Term | State | When you see it | | -------------- | ------------------ | --------------------------------- | | Chromatin | Loose, uncondensed | Interphase (normal cell activity) | | Chromosome | Tightly condensed | Mitosis / Meiosis |

👉 You usually see chromosomes only during cell division.

4) Structure of a replicated chromosome

When a chromosome has been copied (after DNA replication), it looks like an “X” shape:

• Two sister chromatids → identical copies of DNA
• Centromere → region holding sister chromatids together
• Telomeres → protective caps at chromosome ends

Each chromatid contains one complete DNA molecule.

5) Why chromosomes condense

Condensation helps:

• Prevent DNA from breaking
• Prevent tangling
• Ensure accurate separation during cell division

Loose DNA would be impossible to divide correctly.

6) Chromosome number (species-specific)

Each species has a fixed chromosome number.

Examples:

• Humans: 46 chromosomes (23 pairs)

• 22 pairs of autosomes

• 1 pair of sex chromosomes (XX or XY)

This arrangement can be seen in a karyotype.

7) Role in cell division

• Mitosis → chromosomes ensure identical cells
• Meiosis → chromosomes allow genetic variation and formation of gametes

Correct chromosome behavior is essential for life.

8) One-sentence exam definition

A chromosome is a condensed DNA–protein structure that carries genes and ensures accurate DNA distribution during cell division.

中文（配图·深入讲解）

1）什么是染色体（chromosome）

染色体是存在于真核细胞细胞核中、由 DNA 高度压缩形成的结构， 它们携带基因，决定生物的性状和功能。

一句话：

染色体 = 高度压缩的 DNA 信息载体

2）染色体的组成

染色体由：

• DNA
• 蛋白质（主要是组蛋白）

组成。

DNA + 组蛋白 = 染色质 染色质高度凝缩后 → 染色体

3）染色质 vs 染色体（重点）

| 名称 | 状态 | 出现时间 | | ------- | ---- | ------- | | 染色质 | 松散 | 间期 | | 染色体 | 高度压缩 | 有丝/减数分裂 |

👉 平时细胞里看到的是染色质，而不是染色体。

4）复制后染色体的结构（X 形）

复制后的染色体通常呈 X 形，由：

• 两条姐妹染色单体

• DNA 完全相同

• 着丝粒

• 连接两条染色单体

• 端粒

• 保护染色体末端

5）为什么染色体要高度压缩

高度压缩可以：

• 防止 DNA 断裂
• 防止 DNA 缠绕
• 保证分裂时准确分离

6）染色体数目（物种特异性）

不同物种染色体数目固定。

以人类为例：

• 46 条染色体（23 对）

• 22 对常染色体

• 1 对性染色体（XX 或 XY）

这些排列方式称为 核型（karyotype）。

7）染色体在细胞分裂中的作用

• 有丝分裂：产生完全相同的体细胞
• 减数分裂：产生配子并增加遗传多样性

8）一句话考试总结

染色体是由 DNA 和蛋白质组成的高度压缩结构，负责储存和准确分配遗传信息。

如果你需要，我可以把 chromatin → chromosome → homologous → sister chromatids 做成一张 中英对照“遗传结构总览图”，非常适合 Biology 10 / 11 复习。

English (thorough explanation with images)

1) What homologous means (core idea)

Homologous means similar in structure and corresponding in position, but not necessarily identical.

In biology, the term is most commonly used in “homologous chromosomes.”

2) Homologous chromosomes (main usage)

Homologous chromosomes are a pair of chromosomes—one from the mother, one from the father—that:

• Have the same length and shape
• Carry the same genes in the same order (same loci)
• May carry different versions of those genes (alleles)

Example:

• Gene for eye color is at the same location on both chromosomes
• One allele may be brown, the other blue

👉 Same genes, possibly different alleles.

3) Homologous ≠ identical (very important)

Homologous chromosomes are not identical.

| Term | Meaning | | -------------------------- | --------------------------------------------------------------- | | Homologous chromosomes | Same genes, may have different alleles | | Sister chromatids | Identical copies of the same chromosome (after DNA replication) |

This distinction is a common exam trap.

4) Role of homologous chromosomes in meiosis

Homologous chromosomes are essential for meiosis:

Meiosis I (key stage)

• Homologous chromosomes pair up (called synapsis)
• They may exchange segments through crossing over
• This increases genetic variation

Meiosis II

• Sister chromatids separate (not homologous chromosomes)

5) Crossing over (why homologous matters)

During crossing over:

• Only homologous chromosomes can pair accurately
• Corresponding DNA regions swap pieces
• Results in new allele combinations

This explains why siblings are genetically similar but not identical.

6) One-sentence exam definition

Homologous chromosomes are a matching pair of chromosomes with the same genes in the same order, one inherited from each parent.

中文（配图·深入讲解）

1）同源（homologous）是什么意思

同源指的是： 结构相似、位置对应、功能相关，但不一定完全相同。

在生物学中，最常见的用法是 “同源染色体”。

2）什么是同源染色体

同源染色体是一对染色体：

• 一条来自 母亲
• 一条来自 父亲

它们具有：

• 相同的长度和形态
• 相同的基因排列顺序
• 但可能有 不同的等位基因

👉 基因相同，版本可能不同。

3）同源 ≠ 完全一样（考试重点）

很多同学容易混淆：

| 概念 | 含义 | | ---------- | ------------- | | 同源染色体 | 基因相同，等位基因可能不同 | | 姐妹染色单体 | 完全相同的复制品 |

⚠️ 同源染色体 不是复制品。

4）同源染色体在减数分裂中的作用

减数分裂 I（关键）

• 同源染色体发生 联会
• 可能发生 交叉互换
• 产生 遗传多样性

减数分裂 II

• 分离的是 姐妹染色单体
• 同源染色体已在第一次分裂中分开

5）为什么“同源”对遗传很重要

• 只有同源染色体才能 准确配对
• 才能进行 交叉互换
• 才能产生新的基因组合

这正是人类个体差异的来源之一。

6）一句话考试版总结

同源染色体是指来自父母的一对染色体，基因位置相同但等位基因可能不同。

如果你愿意，我可以：

• 把 homologous vs sister chromatids 做成 对照速记表
• 或整理 减数分裂 I / II 高频考点图
• 或直接生成 中英双语 flashcards / HTML 学习卡

English (thorough explanation with images)

1) What chromatin is

Chromatin is the complex of DNA and proteins found in the nucleus of eukaryotic cells. Its job is to package long DNA molecules, protect them, and control which genes are active.

In simple terms: chromatin = DNA + proteins (mostly histones).

2) Why chromatin is necessary

Human DNA is extremely long (≈2 meters per cell). Chromatin allows DNA to:

• Fit inside the nucleus
• Avoid tangling and damage
• Be regulated (turned on/off at the right time)

3) The basic unit: the nucleosome

The fundamental repeating unit of chromatin is the nucleosome.

• 8 histone proteins (H2A, H2B, H3, H4 ×2) form a core
• DNA wraps around this core ~1.7 turns
• Looks like “beads on a string” under a microscope

This structure shortens DNA and provides control points for gene regulation.

4) Levels of chromatin packing

Chromatin becomes increasingly compact through levels:

1. DNA double helix
2. Nucleosomes (beads on a string)
3. Chromatin fiber (more tightly coiled)
4. Condensed chromosome (during cell division)

👉 Chromatin is the loose form; 👉 Chromosomes are the fully condensed form.

5) Two functional types of chromatin

Chromatin exists in two main states:

A) Euchromatin

• Loosely packed
• Genes are active (transcribed)
• Appears lighter under a microscope

B) Heterochromatin

• Densely packed
• Genes are inactive or silenced
• Appears darker
• Often found near centromeres and telomeres

6) Chromatin changes during the cell cycle

• Interphase: DNA is mostly in chromatin form
• Mitosis/Meiosis: chromatin condenses into visible chromosomes
• After division, chromosomes unwind back into chromatin

This is why you usually can’t see chromosomes unless a cell is dividing.

7) One-sentence exam definition

Chromatin is a DNA–protein complex in the nucleus that packages genetic material and regulates gene expression.

中文（配图·深入讲解）

1）什么是染色质（chromatin）

染色质是存在于真核细胞细胞核中的DNA 与蛋白质的复合体。

一句话：

染色质 = DNA + 蛋白质（主要是组蛋白）

它的功能是包装 DNA、保护 DNA、调控基因表达。

2）为什么需要染色质

DNA 非常长，如果不包装：

• 根本装不进细胞核
• 容易断裂、缠绕
• 难以控制哪些基因该表达

染色质解决了以上所有问题。

3）染色质的基本单位：核小体

染色质最基本的结构单位是 核小体（nucleosome）：

• 8 个组蛋白组成核心
• DNA 缠绕在组蛋白外侧
• 显微结构像 “串珠”

这是 DNA 压缩和调控的关键结构。

4）染色质的层级结构

DNA 的压缩是分层进行的：

1. DNA 双螺旋
2. 核小体（串珠状）
3. 染色质纤维
4. 高度压缩形成 染色体

👉 染色质：松散、工作状态 👉 染色体：高度压缩、分裂状态

5）两种功能性染色质（重点）

A）常染色质（Euchromatin）

• 结构 松散
• 基因 正在表达
• 显微镜下颜色 较浅

B）异染色质（Heterochromatin）

• 结构 致密
• 基因 沉默
• 显微镜下颜色 较深
• 常位于 着丝粒、端粒

6）细胞周期中的变化

• 间期（Interphase）：DNA 以染色质形式存在
• 分裂期（有丝/减数分裂）：染色质凝缩成染色体
• 分裂结束后再次松开

这就是为什么平时看不到染色体。

7）一句话考试版总结

染色质是由 DNA 和组蛋白组成的复合结构，既能压缩遗传物质，又能调控基因表达。

如果你需要，我可以：

• 把 chromatin → chromosome 做成 一页中英对照流程图
• 或整理成 Biology 10/11 高频考点 + 易混概念对照表
• 或直接帮你生成 可交互 HTML 学习卡（非常适合复习用）

English (thorough explanation with images)

1) What nitrogenous bases are

Nitrogenous bases are nitrogen-containing organic molecules that form one part of a nucleotide. They are the information-carrying component of DNA and RNA.

In every nucleotide:

• Phosphate + sugar = structure
• Nitrogenous base = information

2) Why they are called “nitrogenous”

They contain nitrogen (N) atoms in ring structures. Nitrogen allows these bases to:

• Form hydrogen bonds
• Pair specifically and predictably

This is essential for accurate DNA replication and RNA transcription.

3) The two major categories (very important)

Nitrogenous bases are divided by ring structure:

A) Purines (double-ring, larger)

• Adenine (A)
• Guanine (G)

👉 Structure: two fused rings

B) Pyrimidines (single-ring, smaller)

• Cytosine (C)
• Thymine (T) → DNA only
• Uracil (U) → RNA only

👉 Structure: one ring

Memory trick:

PURe As Gold → Purines = A, G Pyrimidines are the rest

4) DNA vs RNA nitrogenous bases

| Molecule | Bases used | | -------- | ---------- | | DNA | A, T, C, G | | RNA | A, U, C, G |

Key difference:

• DNA uses thymine (T)
• RNA uses uracil (U)

Uracil lacks a methyl group that thymine has, making RNA:

• Less stable
• Suitable for short-term information use

5) Complementary base pairing (core concept)

Nitrogenous bases pair by hydrogen bonds:

• A pairs with T (DNA) or U (RNA)
• C pairs with G

Hydrogen bonds:

• A–T → 2 hydrogen bonds
• C–G → 3 hydrogen bonds (stronger)

This explains why:

• DNA strands are complementary
• DNA can be copied accurately

6) Where bases sit in DNA/RNA structure

• Bases attach to the 1′ carbon of the sugar
• They stick inward toward the center of the DNA double helix
• The sugar-phosphate backbone stays on the outside

Think:

• Backbone = rails
• Bases = rungs of a ladder

7) One-sentence exam definition

Nitrogenous bases are nitrogen-containing molecules in nucleotides that store genetic information and pair specifically through hydrogen bonding.

中文（配图·深入讲解）

1）什么是含氮碱基（nitrogenous bases）

含氮碱基是含有氮元素的有机分子，是核苷酸的三大组成部分之一。

在核苷酸中：

• 糖 + 磷酸 = 结构
• 含氮碱基 = 遗传信息

2）为什么叫“含氮”

因为它们的环状结构中含有 氮原子（N），这使它们能够：

• 形成 氢键
• 实现 精确配对

这是 DNA 能稳定复制的关键原因。

3）两大类含氮碱基（必考）

根据环的数量分类：

A）嘌呤（Purines，双环，大）

• 腺嘌呤（A）
• 鸟嘌呤（G）

👉 特点：两个相连的环

B）嘧啶（Pyrimidines，单环，小）

• 胞嘧啶（C）
• 胸腺嘧啶（T）（只在 DNA）
• 尿嘧啶（U）（只在 RNA）

👉 特点：一个环

4）DNA 与 RNA 中的碱基区别

| 分子 | 含氮碱基 | | ------- | ------- | | DNA | A、T、C、G | | RNA | A、U、C、G |

关键点：

• DNA 用 T
• RNA 用 U

尿嘧啶比胸腺嘧啶少一个 甲基（–CH₃），因此 RNA 更不稳定，适合“临时使用”。

5）碱基互补配对（核心原理）

含氮碱基通过 氢键配对：

• A–T（DNA） / A–U（RNA）
• C–G

氢键数量：

• A–T：2 个
• C–G：3 个（更牢固）

这就是：

• DNA 双链互补的原因
• 遗传信息能准确复制的原因

6）碱基在 DNA 中的位置

• 碱基连接在糖的 1′ 位碳
• 朝向 DNA 内部
• 糖-磷酸骨架在外侧

形象理解：

• 骨架 = 梯子的两侧
• 碱基 = 梯子的横档

7）一句话考试版总结

含氮碱基是核苷酸中负责储存遗传信息的含氮分子，通过氢键进行特异性互补配对。

如果你愿意，我可以：

• 把这些整理成 Biology 10/11 高频考点速查表
• 或做成 中英对照 flashcards（可导入你现在的学习系统）
• 或画一张 “嘌呤 vs 嘧啶 + 配对”一页图，特别适合考试前快速复习

English (thorough explanation with images)

1) What a nucleotide is

A nucleotide is the basic building block (monomer) of nucleic acids:

• DNA (deoxyribonucleic acid)
• RNA (ribonucleic acid)

If DNA or RNA is a long chain, then nucleotides are the individual units that repeat to form that chain—similar to letters forming words.

2) The three parts of a nucleotide (what you see in the diagrams)

Every nucleotide has three components, clearly shown in the images above:

1. Phosphate group

2. Usually drawn as a circle or “P”

3. Links nucleotides together

4. Gives DNA/RNA an overall negative charge

5. Sugar (5-carbon sugar)

6. Drawn as a pentagon

7. DNA uses deoxyribose (one less oxygen)

8. RNA uses ribose (has an extra –OH group)

9. Nitrogenous base

10. Drawn as a rectangle or hexagon

11. Carries the genetic information

12. Types:

13. A (adenine)

14. G (guanine)
15. C (cytosine)
16. T (thymine, DNA only)
17. U (uracil, RNA only)

3) How nucleotides connect (sugar-phosphate backbone)

From the backbone diagrams:

• The phosphate of one nucleotide bonds to the 3′ carbon of the sugar in the previous nucleotide
• This forms a phosphodiester bond

• The chain always has direction:

• 5′ end → 3′ end

The bases stick outward, while the sugar + phosphate form the strong backbone.

4) DNA vs RNA nucleotides (visible differences)

From the images comparing DNA and RNA:

| Feature | DNA | RNA | | ----------------- | --------------- | --------------- | | Sugar | Deoxyribose | Ribose | | Base unique to it | Thymine (T) | Uracil (U) | | Typical structure | Double-stranded | Single-stranded |

5) Why nucleotides matter

The order of bases along the nucleotide chain stores information:

• Example: A-T-G-C
• This sequence determines genes, proteins, and traits

Complementary pairing:

• DNA: A–T, C–G
• RNA: A–U, C–G

This is why DNA can be copied accurately.

6) One-sentence summary (exam-style)

A nucleotide is a molecule made of a phosphate group, a five-carbon sugar, and a nitrogenous base, and it is the fundamental unit of DNA and RNA.

中文（配合图片的深入讲解）

1）什么是核苷酸（nucleotide）

核苷酸是构成DNA 和 RNA 的最基本单位。 DNA / RNA 就是由大量重复的核苷酸首尾相连形成的长链。

可以理解为：

• 核苷酸 = 积木
• DNA / RNA = 用积木拼成的长结构

2）核苷酸的三大组成部分（看图识结构）

从图片可以清楚看到，每个核苷酸都包含：

1）磷酸基

• 通常画成 圆形或 P
• 负责把核苷酸连接成链
• 使 DNA/RNA 带负电

2）五碳糖

• 画成 五边形
• DNA 中是 脱氧核糖
• RNA 中是 核糖（多一个 –OH）

3）含氮碱基

• 画成 方形或多边形
• 是真正的遗传信息载体
• 包括：A、G、C、T（DNA）、U（RNA）

3）核苷酸如何连接成链（糖-磷酸骨架）

从“骨架”示意图可以看到：

• 一个核苷酸的磷酸
• 与下一个核苷酸糖的 3′ 位碳相连
• 形成 磷酸二酯键

因此 DNA/RNA 有明确方向：

• 5′ 端 → 3′ 端

碱基朝外排列，骨架在内侧。

4）DNA 与 RNA 核苷酸的区别（图中对比）

| 项目 | DNA | RNA | | ---- | ------- | ------ | | 糖 | 脱氧核糖 | 核糖 | | 特有碱基 | T（胸腺嘧啶） | U（尿嘧啶） | | 结构 | 双链 | 单链 |

5）核苷酸的重要性

• 碱基排列顺序 = 遗传信息
• 不同顺序 → 不同基因 → 不同性状

互补配对：

• DNA：A–T，C–G
• RNA：A–U，C–G

这保证了复制和转录的准确性。

6）一句话总结（考试版）

核苷酸是由磷酸、五碳糖和含氮碱基组成的分子，是 DNA 和 RNA 的基本结构单位。

如果你需要，我可以：

• 把这些内容整理成 Biology 10 / 11 速记卡片
• 或做成 中英对照 PPT 教学图
• 或生成 可交互 HTML 学习页面（非常适合你平时用的那套学习系统）

Nuclei（细胞核，复数）— with appropriate images

English (thorough explanation)

1) What nuclei means

Nuclei is the plural of nucleus. A nucleus is a membrane-bound structure in eukaryotic cells that contains most of the cell’s DNA and controls cell activities.

👉 Nuclei = more than one nucleus

2) What the nucleus does

Each nucleus:

• Stores genetic material (DNA)
• Controls gene expression
• Directs cell growth, metabolism, and division
• Coordinates DNA replication and RNA transcription

That’s why the nucleus is often called the cell’s control center.

3) Main parts of a nucleus

• Nuclear envelope: double membrane with pores (controls traffic in/out)
• Chromatin: DNA + proteins (uncondensed form)
• Nucleolus: makes rRNA and ribosome subunits
• Nuclear pores: allow RNA and proteins to pass

4) When do cells have multiple nuclei?

Some cells naturally have more than one nucleus:

• Skeletal muscle cells → multinucleate (many nuclei)
• Certain fungi → multinucleate cells
• Cells after failed cytokinesis → binucleate cells

In these cases, multiple nuclei help meet high metabolic or functional demands.

5) Nuclei during cell division

• Interphase: nucleus is intact; DNA is chromatin

• Mitosis:

• Nuclear envelope breaks down

• Chromosomes separate
• Two new nuclei form in telophase
• Cytokinesis then separates the cell body

So after mitosis, a cell briefly has two nuclei before splitting.

6) Nucleus vs nucleolus vs nuclei (common confusion)

| Term | Meaning | | ------------- | ---------------------------------------------- | | Nucleus | One DNA-containing control center | | Nuclei | Plural of nucleus | | Nucleolus | Structure inside the nucleus (makes ribosomes) |

中文（详细解释）

1）什么是 nuclei

Nuclei 是 nucleus（细胞核） 的复数形式。 细胞核是真核细胞中被膜包裹、储存 DNA 的结构。

👉 Nuclei = 多个细胞核

2）细胞核的作用

每个细胞核：

• 储存遗传信息（DNA）
• 控制基因表达
• 调控细胞生长、代谢和分裂
• 负责 DNA 复制 和 RNA 转录

因此细胞核常被称为“细胞的控制中心”。

3）细胞核的主要结构

• 核膜：双层膜，有核孔
• 染色质：DNA + 蛋白质
• 核仁：合成 rRNA，组装核糖体
• 核孔：物质进出通道

4）什么时候细胞会有多个细胞核？

一些细胞天然多核：

• 骨骼肌细胞：多个细胞核
• 某些真菌细胞
• 细胞质分裂失败后形成的双核细胞

多核结构可以支持高能量或高蛋白合成需求。

5）细胞分裂中的细胞核变化

• 间期：细胞核完整

• 有丝分裂：

• 核膜消失

• 染色体分离
• 末期形成 两个新细胞核
• 细胞质分裂后形成两个独立细胞

6）易混概念对比

| 词汇 | 含义 | | ------------- | ------- | | Nucleus | 一个细胞核 | | Nuclei | 多个细胞核 | | Nucleolus | 细胞核内部结构 |

一句话总结（双语）

• Nuclei = plural of nucleus
• Nuclei = 多个细胞核

如果你愿意，我可以继续帮你： ✔️ 对比 nucleus vs nucleolus ✔️ 解释 多核细胞为什么不分裂 ✔️ 出 Biology 10/11 高频判断题

Complementary bases（互补碱基）— with appropriate images

English (thorough explanation)

1) What “complementary bases” means

Complementary bases are pairs of bases in DNA or RNA that match specifically because their shapes and hydrogen-bonding patterns fit together. This precise matching lets cells store and copy genetic information accurately.

2) The pairing rules

• DNA: A–T and C–G
• RNA: A–U and C–G

Example: If one DNA strand is A–C–G–T, the complementary strand is T–G–C–A.

3) Why these pairs work

• Hydrogen bonds:

• A–T (or A–U) form 2 hydrogen bonds

• C–G form 3 hydrogen bonds (stronger)
• Size matching: A purine (large, 2 rings) pairs with a pyrimidine (small, 1 ring), keeping the helix width uniform.

4) Why complementary bases matter

• DNA replication: Each original strand serves as a template; complementary bases build the new strand.
• Transcription & translation: RNA is synthesized using complementary pairing, and tRNA anticodons pair with mRNA codons to add correct amino acids.
• Stability: GC-rich regions are often more stable because C–G has 3 hydrogen bonds.

中文（详细解释）

1）什么是“互补碱基”

互补碱基是指 DNA 或 RNA 中的碱基按照固定规则成对结合，因为它们的空间结构和氢键分布刚好匹配，从而保证遗传信息稳定、准确地复制与表达。

2）配对规则

• DNA：A–T，C–G
• RNA：A–U，C–G

例子： 一条 DNA 链为 A–C–G–T，其互补链为 T–G–C–A。

3）为什么这样配对

• 氢键数量：

• A–T / A–U：2 条

• C–G：3 条（更稳定）
• 大小匹配： 嘌呤（大，双环）与嘧啶（小，单环）配对，使 DNA 双螺旋宽度一致。

4）互补碱基的重要性

• DNA 复制： 原链作模板，按互补规则合成新链。
• 转录与翻译： RNA 合成与密码子识别都依赖互补配对。
• 稳定性： GC 含量高的区域通常更难被分开。

如果你需要，我可以把这些内容整理成双语闪卡（Q/A/解释）或做一个交互式 HTML 图示，方便教学或复习。

Meiosis（减数分裂）— with appropriate images

English (thorough explanation)

1) What meiosis is (core idea)

Meiosis is a special type of cell division that produces gametes (sex cells) with half the number of chromosomes of the parent cell. It is essential for sexual reproduction and genetic diversity.

👉 Meiosis = making sex cells with half the chromosomes

2) Why meiosis is necessary

Meiosis:

• Reduces chromosome number (diploid → haploid)
• Prevents chromosome numbers from doubling every generation
• Creates genetic variation, which supports evolution

Human example:

• Body cells: 46 chromosomes (2n)
• Gametes: 23 chromosomes (n)
• Fertilization restores 46 (n + n → 2n)

3) Two divisions, one DNA replication

DNA is copied once (during interphase), but the cell divides twice:

• Meiosis I – reduction division
• Meiosis II – separation of sister chromatids

4) Meiosis I (reduction division — the key stage)

Meiosis I reduces the chromosome number by half.

Major events:

• Prophase I:

• Homologous chromosomes pair (synapsis)

• Crossing over occurs (DNA exchange)

• Metaphase I:

• Homologous pairs line up at the equator

• Anaphase I:

• Homologous chromosomes separate

• Telophase I:

• Two haploid cells form (chromosomes still duplicated)

5) Meiosis II (similar to mitosis)

Meiosis II separates sister chromatids.

Result:

• Four haploid cells
• All are genetically different

6) Sources of genetic variation

Meiosis creates variation through:

1. Crossing over (Prophase I)
2. Independent assortment of chromosomes
3. Random fertilization

This is why siblings are genetically unique.

7) Meiosis vs mitosis (common exam comparison)

| Feature | Meiosis | Mitosis | | ----------------- | ------------------- | --------------- | | Divisions | 2 | 1 | | Daughter cells | 4 | 2 | | Chromosome number | Half (n) | Same (2n) | | Genetic makeup | Different | Identical | | Purpose | Sexual reproduction | Growth & repair |

中文（详细解释）

1）什么是减数分裂（Meiosis）

减数分裂是一种形成性细胞（精子和卵子）的细胞分裂方式，其结果是染色体数目减半。

👉 减数分裂 = 产生单倍体性细胞

2）为什么需要减数分裂

减数分裂的作用：

• 将染色体数减半
• 防止染色体数代代翻倍
• 产生遗传多样性

人类例子：

• 体细胞：46 条染色体
• 配子：23 条
• 受精后恢复为 46 条

3）一次复制，两次分裂

• DNA 只复制 一次
• 细胞分裂 两次（减 I、减 II）

4）减数分裂 I（最关键）

减数分裂 I 的主要特点是同源染色体分离。

关键过程：

• 前期 I： 同源染色体配对，发生交叉互换
• 中期 I： 同源染色体对排列在中央
• 后期 I： 同源染色体分离
• 末期 I： 形成两个单倍体细胞

5）减数分裂 II

过程类似于有丝分裂：

• 姐妹染色单体分离
• 形成 4 个单倍体细胞
• 每个细胞的遗传信息都不同

6）遗传多样性的来源

• 交叉互换
• 自由组合
• 随机受精

7）减数分裂 vs 有丝分裂（考试重点）

| 项目 | 减数分裂 | 有丝分裂 | | ---- | ---- | ----- | | 分裂次数 | 2 | 1 | | 子细胞数 | 4 | 2 | | 染色体数 | 减半 | 不变 | | 遗传信息 | 不同 | 相同 | | 作用 | 生殖 | 生长、修复 |

一句话总结（双语）

• Meiosis = cell division that produces haploid gametes
• 减数分裂 = 产生单倍体性细胞并增加遗传多样性的分裂方式

如果你愿意，我可以继续帮你做 ✔️ PMAT × 2（减 I / 减 II）速记图 ✔️ Biology 10/11 高频判断题 ✔️ 可打印或交互式示意图

Sperm（精子）— with appropriate images

English (thorough explanation)

1) What sperm is (core definition)

Sperm is the male gamete (sex cell) used in sexual reproduction. Its role is to deliver male genetic information to the egg during fertilization.

In simple terms: 👉 Sperm = male sex cell that carries DNA to the egg

2) Chromosome number

• Sperm cells are haploid (n)
• They contain half the normal number of chromosomes

Example (humans):

• Sperm: 23 chromosomes
• Egg: 23 chromosomes
• Fertilization → zygote with 46 chromosomes

3) Structure of a sperm cell

A sperm cell has three main parts, each with a specific function:

• Head

• Contains the nucleus (DNA)

• Covered by the acrosome, which has enzymes to penetrate the egg

• Midpiece

• Packed with mitochondria

• Produces energy (ATP) for movement

• Tail (flagellum)

• Enables the sperm to swim toward the egg

This streamlined shape is adapted for speed and mobility.

4) How sperm are produced

Sperm are produced in the testes through spermatogenesis:

• Starts from diploid cells
• Uses meiosis
• Produces four haploid sperm cells
• Occurs continuously after puberty

5) Role of sperm in fertilization

During fertilization:

1. Sperm swim toward the egg
2. One sperm penetrates the egg membrane
3. The nuclei fuse
4. A diploid zygote forms

Only one sperm normally fertilizes the egg.

6) Why sperm are important

Sperm:

• Enable sexual reproduction
• Contribute genetic diversity
• Determine the biological sex of offspring in humans (X or Y chromosome)

中文（详细解释）

1）什么是精子（Sperm）

精子是用于有性生殖的雄性配子。 它的主要作用是将父方的遗传信息传递给卵细胞。

一句话： 👉 精子 = 携带遗传信息的雄性性细胞

2）染色体数目

• 精子是单倍体（n）
• 只含一半染色体

人类例子：

• 精子：23 条
• 卵子：23 条
• 受精后：46 条（合子）

3）精子的结构

精子主要由三部分组成：

• 头部

• 含细胞核（DNA）

• 有顶体，释放酶帮助进入卵子

• 中段

• 富含线粒体

• 提供运动能量

• 尾部

• 帮助精子游动

4）精子的产生

精子在睾丸中通过精子发生（减数分裂）产生：

• 每个原始细胞可形成 4 个精子
• 从青春期后持续进行

5）精子在受精中的作用

受精过程：

• 精子进入卵细胞
• 细胞核融合
• 形成二倍体合子

6）精子的重要性

精子：

• 实现有性生殖
• 增加遗传多样性
• 决定后代的生理性别（X 或 Y）

一句话总结（双语）

• Sperm = the male haploid gamete
• 精子 = 单倍体的雄性配子

如果你需要，我可以继续帮你做 ✔️ sperm vs egg 对照表 ✔️ Biology 10/11 易错点速记 ✔️ 双语闪卡（结构 + 功能）

Diploid（二倍体）— with appropriate images

English (thorough explanation)

1) What diploid means (core definition)

Diploid describes a cell that contains two complete sets of chromosomes, written as 2n—one set inherited from each parent.

In simple terms: 👉 Diploid = two sets of chromosomes

2) Diploid vs haploid (key comparison)

• Diploid (2n): two sets of chromosomes
• Haploid (n): one set of chromosomes

Example (humans):

• Diploid cells: 46 chromosomes (23 pairs)
• Haploid cells (gametes): 23 chromosomes

3) Which cells are diploid

In most animals and plants:

• Somatic (body) cells are diploid (skin, muscle, nerve cells)
• Zygote (fertilized egg) is diploid
• Gametes (sperm/egg) are not diploid—they are haploid

4) Why two sets matter

Having two sets of chromosomes means:

• Genes come in pairs (homologous chromosomes)
• Different alleles can interact (dominant/recessive)
• One copy can sometimes compensate if the other has a mutation

5) How diploid cells are formed

• Fertilization: haploid sperm (n) + haploid egg (n) → diploid zygote (2n)
• Mitosis: diploid cells divide to make two identical diploid cells

6) Diploid cells in the life cycle

Typical sexual life cycle:

1. Diploid organism (2n)
2. Meiosis → haploid gametes (n)
3. Fertilization → diploid zygote (2n)
4. Mitosis → growth and repair (2n)

7) Common exam mistakes

• Thinking diploid means “double-sized chromosomes” ❌
• Confusing diploid with paired chromatids ❌
• Forgetting that diploid refers to sets, not cell size ❌

中文（详细解释）

1）什么是二倍体（Diploid）

二倍体指的是：细胞中含有两整套染色体，用 2n 表示，其中一套来自父方，一套来自母方。

一句话： 👉 二倍体 = 含两套染色体的细胞

2）二倍体 vs 单倍体（考试重点）

• 二倍体（2n）：两套染色体
• 单倍体（n）：一套染色体

人类例子：

• 二倍体细胞：46 条染色体
• 单倍体细胞（配子）：23 条染色体

3）哪些细胞是二倍体

• 体细胞（皮肤、肌肉、神经等）
• 合子（受精卵）

⚠️ 精子和卵子是单倍体，不是二倍体。

4）为什么要有两套染色体

两套染色体的意义：

• 基因成对存在（同源染色体）
• 等位基因相互作用
• 可降低某些突变带来的影响

5）二倍体如何形成与维持

• 受精：n + n → 2n
• 有丝分裂：2n → 2n（生长与修复）

6）生命周期中的二倍体

有性生殖的典型过程：

• 二倍体个体 → 减数分裂 → 单倍体配子
• 配子受精 → 二倍体合子
• 有丝分裂 → 个体生长

一句话总结（双语）

• Diploid = two sets of chromosomes (2n)
• 二倍体 = 含两套染色体的细胞

如果你需要，我可以继续帮你做 ✔️ haploid vs diploid vs polyploid 对照表 ✔️ Biology 10/11 高频判断题 ✔️ 双语闪卡（定义 + 易错点）

Haploid（单倍体）— with appropriate images

English (thorough explanation)

1) What haploid means (core definition)

Haploid describes a cell that contains one complete set of chromosomes, written as n.

In simple terms: 👉 Haploid = one set of chromosomes

2) Haploid vs diploid (key comparison)

• Haploid (n) → one set of chromosomes
• Diploid (2n) → two sets of chromosomes (one from each parent)

Example (humans):

• Haploid cells: 23 chromosomes
• Diploid cells: 46 chromosomes

3) Which cells are haploid

In most animals and plants:

• Gametes (sex cells) are haploid

• Sperm

• Egg (ovum)

All other body cells (somatic cells) are diploid.

4) How haploid cells are made

Haploid cells are produced by meiosis:

• One diploid cell undergoes meiosis
• Chromosome number is reduced by half
• Four haploid cells are produced

This reduction is essential for sexual reproduction.

5) Haploid cells and fertilization

During fertilization:

• One haploid sperm (n)
• • one haploid egg (n)
• → diploid zygote (2n)

This restores the full chromosome number in the new organism.

6) Why haploid cells are important

Haploid cells:

• Prevent chromosome numbers from doubling each generation
• Allow genetic variation
• Make sexual reproduction possible

Without haploid cells, species could not maintain a stable genome.

7) Common exam mistakes

• Thinking haploid means “half a chromosome” ❌
• Thinking all small cells are haploid ❌
• Forgetting that haploid refers to sets, not size ❌

中文（详细解释）

1）什么是单倍体（Haploid）

单倍体指的是：细胞中只有一整套染色体，用 n 表示。

一句话： 👉 单倍体 = 只有一套染色体

2）单倍体 vs 二倍体（考试重点）

• 单倍体（n）：一套染色体
• 二倍体（2n）：两套染色体（父母各一套）

人类例子：

• 单倍体：23 条染色体
• 二倍体：46 条染色体

3）哪些细胞是单倍体

通常只有配子是单倍体：

• 精子
• 卵子

身体的其他细胞（体细胞）都是二倍体。

4）单倍体细胞如何形成

单倍体细胞通过减数分裂形成：

• 染色体数量减半
• 产生 4 个单倍体细胞

5）单倍体与受精

在受精过程中：

• 单倍体精子（n）
• 单倍体卵子（n）
• 结合形成二倍体合子（2n）

6）为什么单倍体很重要

单倍体细胞：

• 维持物种染色体数稳定
• 增加遗传多样性
• 是有性生殖的基础

一句话总结（双语）

• Haploid = one set of chromosomes (n)
• 单倍体 = 含一套染色体的细胞

如果你愿意，我可以继续帮你做 ✔️ haploid vs diploid vs polyploid 对照表 ✔️ Biology 10/11 高频判断题 ✔️ 双语闪卡（定义 + 易错点）

Gamete（配子）— with appropriate images

English (thorough explanation)

1) What a gamete is (core definition)

A gamete is a sex cell used in sexual reproduction. Gametes carry half the normal number of chromosomes and combine during fertilization to form a zygote.

In simple terms: 👉 Gamete = a sex cell with half the chromosomes

2) Types of gametes

There are two main types:

• Sperm (male gamete)
• Egg / ovum (female gamete)

Key differences:

• Sperm → small, mobile, produced in large numbers
• Egg → large, non-mobile, contains nutrients for early development

3) Chromosome number (haploid)

Gametes are haploid (n):

• They contain one set of chromosomes
• This is achieved through meiosis

Example (humans):

• Body cells: 46 chromosomes (diploid, 2n)
• Gametes: 23 chromosomes (haploid, n)

4) Gametes and fertilization

During fertilization:

• One sperm + one egg fuse
• Their nuclei combine
• A diploid zygote (2n) is formed

This restores the full chromosome number and creates a genetically unique individual.

5) Why gametes are important

Gametes:

• Enable sexual reproduction
• Maintain a constant chromosome number across generations
• Create genetic variation, which supports evolution

Without gametes, complex sexual reproduction would not be possible.

6) Gamete vs zygote vs somatic cell (common confusion)

| Term | Description | Chromosomes | | ---------------- | -------------------- | ------------ | | Gamete | Sex cell (sperm/egg) | Haploid (n) | | Zygote | Fertilized egg | Diploid (2n) | | Somatic cell | Body cell | Diploid (2n) |

中文（详细解释）

1）什么是配子（Gamete）

配子是用于有性生殖的性细胞。 它只含有一半的染色体数目，在受精时与另一配子结合形成合子。

一句话： 👉 配子 = 含一半染色体的性细胞

2）配子的类型

主要有两种配子：

• 精子（雄性配子）
• 卵细胞 / 卵子（雌性配子）

特点对比：

• 精子：体积小、能运动、数量多
• 卵子：体积大、不能运动、含营养物质

3）染色体数目（单倍体）

配子是单倍体（n）：

• 只含一套染色体
• 通过减数分裂形成

人类例子：

• 体细胞：46 条（2n）
• 配子：23 条（n）

4）配子与受精

在受精过程中：

• 一个精子与一个卵子结合
• 形成二倍体合子

这是新生命的起点。

5）为什么配子很重要

配子：

• 实现有性生殖
• 保持物种染色体数稳定
• 增加遗传多样性

6）易混概念对比

| 概念 | 含义 | 染色体 | | ------- | ---- | --- | | 配子 | 性细胞 | 单倍体 | | 合子 | 受精卵 | 二倍体 | | 体细胞 | 普通细胞 | 二倍体 |

一句话总结（双语）

• Gamete = a haploid sex cell
• 配子 = 含一半染色体的性细胞

如果你需要，我可以继续帮你做 ✔️ gamete → zygote → embryo 流程图 ✔️ Biology 10/11 常考判断题 ✔️ 双语闪卡（定义 + 对比练习）

Zygote（合子 / 受精卵）— with appropriate images

English (thorough explanation)

1) What a zygote is (core definition)

A zygote is the single cell formed when a sperm cell fuses with an egg cell during fertilization.

In simple terms: 👉 Zygote = the very first cell of a new organism

2) How a zygote is formed

• Sperm and egg are haploid (n), meaning they each carry half the chromosome number
• During fertilization, their nuclei merge
• The result is a diploid (2n) zygote

Example (humans):

• Sperm: 23 chromosomes
• Egg: 23 chromosomes
• Zygote: 46 chromosomes

3) Why the zygote is important

The zygote:

• Contains a complete set of genetic information
• Has a unique DNA combination
• Is the starting point for growth and development

Every cell in the organism develops from this one cell through mitosis.

4) What happens after the zygote forms

After fertilization, the zygote:

1. Begins mitotic divisions (cleavage)
2. Becomes a multicellular embryo
3. Continues development into a fetus and eventually a mature organism

At this stage:

• Cell number increases
• Cell size does not initially increase

5) Zygote vs gamete vs embryo (common confusion)

| Term | Meaning | | ---------- | ----------------------------------- | | Gamete | Sex cell (sperm or egg), haploid | | Zygote | Fertilized egg, diploid | | Embryo | Multicellular stage after divisions |

中文（详细解释）

1）什么是合子（Zygote / 受精卵）

合子是精子与卵细胞结合后形成的第一个细胞，标志着一个新生命的开始。

一句话： 👉 合子 = 新个体的第一个细胞

2）合子的形成过程

• 精子和卵细胞都是单倍体（n）
• 各自只含一半染色体
• 受精时，细胞核融合
• 形成二倍体（2n）合子

人类例子：

• 精子：23 条染色体
• 卵子：23 条染色体
• 合子：46 条染色体

3）为什么合子很重要

合子：

• 拥有完整的遗传信息
• DNA 组合独一无二
• 是生长、发育和分化的起点

所有体细胞都来源于合子的有丝分裂。

4）合子之后会发生什么

合子形成后会：

1. 进行快速有丝分裂（卵裂）
2. 形成多细胞胚胎
3. 继续发育成胎儿和成体

早期阶段：

• 细胞数增加
• 总体体积几乎不变

5）易混概念对比

| 概念 | 含义 | | ------ | ------------ | | 配子 | 精子 / 卵子（单倍体） | | 合子 | 受精卵（二倍体） | | 胚胎 | 多细胞阶段 |

一句话总结（双语）

• Zygote = a fertilized egg cell
• 合子 = 精子与卵子结合形成的第一个细胞

如果你需要，我可以继续帮你做 ✔️ meiosis → fertilization → mitosis 流程图 ✔️ Biology 10/11 易错点练习 ✔️ 双语闪卡（定义 + 判断题）

Crossing over（交叉互换）— with appropriate images

English (thorough explanation)

1) What crossing over is (core idea)

Crossing over is the exchange of DNA segments between homologous chromosomes during prophase I of meiosis.

In simple terms: 👉 Crossing over = swapping DNA between matching chromosomes

This process creates new combinations of genes, increasing genetic variation.

2) When and where it happens

• Occurs during Prophase I of Meiosis I
• Happens after homologous chromosomes pair up (synapsis)
• The paired structure is called a tetrad (4 chromatids total)

The visible crossover points are called chiasmata (singular: chiasma).

3) How crossing over works (step-by-step)

1. Homologous chromosomes pair closely along their lengths
2. Non-sister chromatids touch at matching gene regions
3. DNA breaks and rejoins, exchanging equivalent segments
4. Chromosomes separate with new allele combinations

⚠️ Only non-sister chromatids exchange DNA—not sister chromatids.

4) Why crossing over is important

Crossing over:

• Increases genetic diversity among gametes
• Produces offspring that are genetically unique
• Helps proper alignment and separation of homologous chromosomes

Without crossing over:

• Less variation
• Higher risk of chromosome separation errors

5) Crossing over vs independent assortment (don’t confuse)

• Crossing over → recombination within a chromosome pair
• Independent assortment → random separation of different chromosome pairs

Both contribute to genetic diversity, but in different ways.

6) Common exam mistakes

• Saying it occurs in mitosis ❌
• Saying it happens in meiosis II ❌
• Mixing up homologous chromosomes with sister chromatids ❌

Correct statement: ✔️ Crossing over occurs between non-sister chromatids of homologous chromosomes during prophase I.

中文（详细解释）

1）什么是交叉互换（Crossing over）

交叉互换是指在减数分裂 I 的前期（Prophase I）， 同源染色体之间交换 DNA 片段的过程。

一句话： 👉 交叉互换 = 同源染色体之间“交换基因片段”

2）发生的时间和位置

• 发生在减数分裂 I 的前期
• 同源染色体配对后发生
• 四条染色单体形成一个四分体
• 交叉点称为交叉点 / 交叉节（chiasmata）

3）交叉互换如何进行（步骤）

1. 同源染色体紧密配对
2. 非姐妹染色单体在相同基因位置接触
3. DNA 断裂并重新连接
4. 形成新的等位基因组合

⚠️ 发生交换的是非姐妹染色单体，不是姐妹染色单体。

4）交叉互换的重要性

交叉互换可以：

• 增加遗传多样性
• 使每个配子都独一无二
• 帮助同源染色体正确分离

5）交叉互换 vs 自由组合（易混点）

• 交叉互换：同一对染色体内部交换
• 自由组合：不同染色体对随机分配

二者都是遗传多样性的来源。

6）考试常见错误

❌ 发生在有丝分裂 ❌ 发生在减数分裂 II ❌ 姐妹染色单体之间交换

✔️ 正确表述： 交叉互换发生在减数分裂 I 前期的同源染色体非姐妹染色单体之间

一句话总结（双语）

• Crossing over = exchange of DNA between homologous chromosomes
• 交叉互换 = 同源染色体之间的基因交换

如果你需要，我可以继续帮你做 ✔️ Crossing over vs independent assortment 对照表 ✔️ Biology 10/11 常考判断题 ✔️ 可打印或交互式标注示意图

Homologous（同源的／同源染色体）— with appropriate images

English (thorough explanation)

1) What homologous means (core idea)

Homologous means corresponding or matching in structure and function because of shared origin.

In genetics, it most commonly refers to homologous chromosomes:

• A pair of chromosomes, one inherited from the mother and one from the father
• They carry the same genes in the same order, but may have different alleles

In simple terms: 👉 Homologous = same type, same genes, different versions possible

2) Homologous chromosomes explained

A pair of homologous chromosomes:

• Are the same size and shape
• Have the same centromere position
• Carry genes for the same traits
• Can have different alleles (e.g., A vs a)

Example:

• One chromosome may carry brown-eye allele
• The other may carry blue-eye allele

They are homologous because they control the same trait, even if the versions differ.

3) Homologous vs sister chromatids (very common confusion)

| Feature | Homologous Chromosomes | Sister Chromatids | | --------------- | -------------------------------------- | ----------------------------- | | Origin | One from each parent | Copies of the same chromosome | | Genetic content | Same genes, possibly different alleles | Identical DNA | | When paired | Meiosis I | After DNA replication | | Separate during | Meiosis I | Mitosis & Meiosis II |

👉 Homologous ≠ identical

4) Role of homologous chromosomes in meiosis

Homologous chromosomes are crucial in meiosis I:

• They pair up (synapsis)
• Crossing over occurs (exchange of DNA)
• They separate into different cells

This process:

• Reduces chromosome number by half
• Creates genetic variation

5) Homologous structures (broader meaning)

Outside genetics, homologous can also mean:

• Structures with shared evolutionary origin

Examples:

• Human arm & whale flipper
• Bat wing & human hand

They look different but come from the same ancestral structure.

中文（详细解释）

1）什么是Homologous（同源的）

homologous 的意思是： 👉 来源相同、结构和功能相对应

在遗传学中，最常见的是同源染色体：

• 一条来自母亲
• 一条来自父亲
• 控制相同的性状
• 但可能携带不同等位基因

一句话： 👉 同源 = 基因位置相同，但版本可能不同

2）同源染色体是什么

一对同源染色体具有：

• 相同的大小和形状
• 相同的着丝点位置
• 控制相同的性状
• 等位基因可能不同

例子：

• 一条带棕眼基因
• 一条带蓝眼基因

3）同源染色体 vs 姐妹染色单体（考试重点）

| 对比 | 同源染色体 | 姐妹染色单体 | | -------- | ------ | -------------- | | 来源 | 父母各一条 | 同一条染色体复制 | | DNA 是否相同 | 不一定 | 完全相同 | | 出现阶段 | 减数分裂 I | 复制后 | | 分离阶段 | 减数分裂 I | 有丝分裂 / 减数分裂 II |

⚠️ 同源 ≠ 相同

4）同源染色体在减数分裂中的作用

在减数分裂 I中：

• 同源染色体配对
• 发生交叉互换
• 被分到不同子细胞中

这是遗传多样性的关键来源。

5）homologous 的扩展含义

在进化生物学中，homologous 还指：

• 同源结构（起源相同）

例子：

• 人类的手臂
• 鲸鱼的鳍
• 蝙蝠的翅膀

一句话总结（双语）

• Homologous = same type, same genes, different versions
• 同源 = 控制相同性状，但基因版本可能不同

如果你需要，我可以继续帮你做 ✔️ homologous vs analogous vs sister chromatids 对比表 ✔️ Biology 10/11 易错点练习 ✔️ 双语闪卡（定义 + 判断题）

Meiosis（减数分裂）— with appropriate images

English (thorough explanation)

1) What meiosis is (core idea)

Meiosis is a special type of cell division that produces gametes (sex cells) with half the number of chromosomes of the parent cell.

• Occurs in ovaries and testes
• Produces sperm and eggs
• Creates genetic diversity

In simple terms: 👉 Meiosis = making sex cells with half the chromosomes

2) Why meiosis is necessary

Meiosis is essential because:

• It halves the chromosome number
• Prevents chromosome numbers from doubling every generation
• Creates variation, which is important for evolution

Example (humans):

• Body cells: 46 chromosomes
• Gametes: 23 chromosomes
• Fertilization: 23 + 23 = 46

3) Two divisions: Meiosis I and Meiosis II

Meiosis has two rounds of division, but DNA is copied only once (before meiosis begins).

4) Meiosis I (reduction division)

This division reduces chromosome number.

Key events:

• Homologous chromosomes pair up

• Crossing over occurs

• Exchange of DNA between homologous chromosomes

• Homologous chromosomes separate

Result after Meiosis I:

• Two cells
• Each has half the chromosomes, but chromosomes are still duplicated

5) Meiosis II (similar to mitosis)

This division separates sister chromatids.

Key events:

• Chromosomes line up individually
• Sister chromatids separate
• Four cells are produced

Result after Meiosis II:

• Four haploid cells
• All genetically different

6) Sources of genetic variation

Meiosis creates variation through:

1. Crossing over (Prophase I)
2. Independent assortment of chromosomes
3. Random fertilization

This is why siblings (except identical twins) are genetically unique.

7) Meiosis vs mitosis (very common comparison)

| Feature | Meiosis | Mitosis | | ----------------- | ------------------- | --------------- | | Divisions | 2 | 1 | | Daughter cells | 4 | 2 | | Chromosome number | Half | Same | | Genetic makeup | Different | Identical | | Purpose | Sexual reproduction | Growth & repair |

中文（详细解释）

1）什么是减数分裂（Meiosis）

减数分裂是一种形成性细胞（精子和卵细胞）的细胞分裂方式，其结果是染色体数量减半。

一句话： 👉 减数分裂 = 产生染色体数量减半的性细胞

2）为什么需要减数分裂

减数分裂的作用包括：

• 将染色体数量减半
• 保证代代相同的染色体数
• 增加遗传多样性

人类例子：

• 体细胞：46 条染色体
• 性细胞：23 条
• 受精后恢复为 46 条

3）减数分裂的两次分裂

减数分裂包含：

• 减数分裂 I
• 减数分裂 II

DNA 只复制一次，但细胞分裂两次。

4）减数分裂 I（关键阶段）

这是最重要的一次分裂。

主要特点：

• 同源染色体配对
• 发生交叉互换
• 同源染色体分离
• 染色体数减半

5）减数分裂 II

过程类似于有丝分裂。

主要特点：

• 姐妹染色单体分离
• 形成 4 个单倍体细胞
• 每个细胞都不同

6）遗传多样性的来源

• 交叉互换
• 自由组合
• 随机受精

这是后代差异的根本原因。

7）减数分裂 vs 有丝分裂（考试重点）

| 项目 | 减数分裂 | 有丝分裂 | | ---- | ---- | ----- | | 分裂次数 | 2 | 1 | | 子细胞数 | 4 | 2 | | 染色体数 | 减半 | 不变 | | 遗传信息 | 不同 | 相同 | | 作用 | 生殖 | 生长、修复 |

一句话总结（双语）

• Meiosis = cell division for sexual reproduction
• 减数分裂 = 形成性细胞并产生遗传多样性的分裂方式

如果你需要，我可以继续帮你做 ✔️ PMAT × 2（Meiosis I / II）对照表 ✔️ Biology 10/11 常考比较题 ✔️ 交互式“染色体移动”动画讲解

Chromosomes（染色体）— with appropriate images

English (thorough explanation)

1) What chromosomes are (core definition)

Chromosomes are structures made of DNA and proteins that carry genes. They package long DNA molecules so genetic information can be stored, copied, and distributed accurately during cell division.

In simple terms: 👉 Chromosomes = organized DNA packages that carry genes

2) What chromosomes are made of

Each chromosome consists of:

• DNA → genetic instructions
• Proteins (histones) → help coil and organize DNA

DNA wraps around histones to form chromatin. When a cell is dividing, chromatin condenses into visible chromosomes.

3) Chromatin vs chromosome (common confusion)

• Chromatin:

• Long, thin, uncoiled DNA

• Seen during interphase

• Chromosome:

• Short, thick, condensed DNA

• Seen during mitosis or meiosis

They are the same material, just in different forms.

4) Structure of a duplicated chromosome

After DNA replication (S phase), one chromosome has:

• Two sister chromatids (identical copies)
• Joined at a centromere

During anaphase, sister chromatids separate and become individual chromosomes.

5) Number of chromosomes (species-specific)

Each species has a characteristic chromosome number.

Examples:

• Humans: 46 chromosomes (23 pairs)
• Dogs: 78 chromosomes
• Fruit flies: 8 chromosomes

In humans:

• 22 pairs = autosomes
• 1 pair = sex chromosomes (XX or XY)

6) Why chromosomes are important

Chromosomes:

• Ensure accurate DNA replication
• Guarantee equal distribution of genes to daughter cells
• Allow inheritance of traits
• Help scientists detect genetic disorders (e.g., missing or extra chromosomes)

中文（详细解释）

1）什么是染色体（Chromosomes）

染色体是由 DNA 和蛋白质组成的结构，负责携带基因。

一句话： 👉 染色体 = DNA 的“打包形式”，用于携带遗传信息

2）染色体的组成

染色体由以下成分构成：

• DNA：遗传信息
• 蛋白质（组蛋白）：帮助 DNA 折叠和缠绕

DNA 缠绕蛋白质形成染色质，在细胞分裂时进一步压缩成染色体。

3）染色质 vs 染色体（考试重点）

• 染色质：

• 松散、细长

• 存在于间期

• 染色体：

• 浓缩、短粗

• 存在于细胞分裂期

本质相同，只是状态不同。

4）复制后染色体的结构

DNA 复制后，一条染色体包括：

• 两条姐妹染色单体
• 通过着丝点连接

在后期，姐妹染色单体分离，成为独立染色体。

5）染色体数量

不同物种的染色体数量不同。

例子：

• 人类：46 条（23 对）
• 果蝇：8 条

人类中：

• 22 对为常染色体
• 1 对为性染色体（XX 或 XY）

6）为什么染色体很重要

染色体可以：

• 确保 DNA 正确复制
• 保证遗传信息平均分配
• 决定性状的遗传
• 帮助检测遗传异常

一句话总结（双语）

• Chromosomes = condensed DNA carrying genes
• 染色体 = 携带基因的高度压缩 DNA 结构

如果你需要，我可以继续帮你做 ✔️ Biology 10/11 染色体速记卡 ✔️ chromatin vs chromosome 对比表 ✔️ 可打印标注图或交互式学习页

Cytokinesis（细胞质分裂）— with appropriate images

English (thorough explanation)

1) What cytokinesis is (core idea)

Cytokinesis is the final step of cell division in which the cytoplasm splits, producing two separate daughter cells.

In simple terms: 👉 Cytokinesis = the cell actually splits into two

It usually overlaps with or follows telophase of mitosis.

2) How cytokinesis fits in the cell cycle

• Interphase → cell grows and copies DNA
• Mitosis → nucleus divides
• Cytokinesis → cytoplasm divides

⚠️ Mitosis divides the nucleus; cytokinesis divides the cell body.

3) Cytokinesis in animal cells

In animal cells, cytokinesis occurs by cleavage:

• A cleavage furrow forms at the center of the cell
• The cell membrane pinches inward
• A ring of actin and myosin contracts (similar to muscle contraction)
• The cell splits into two

This process is fast and flexible because animal cells do not have cell walls.

4) Cytokinesis in plant cells

In plant cells, cytokinesis is different because of the rigid cell wall:

• Vesicles from the Golgi apparatus gather in the center
• They fuse to form a cell plate
• The cell plate grows outward
• It becomes a new cell wall separating the two cells

5) Key differences: animal vs plant cytokinesis

| Feature | Animal Cells | Plant Cells | | ---------------- | --------------- | -------------------- | | Method | Cleavage furrow | Cell plate formation | | Cell wall | ❌ No | ✅ Yes | | Structure formed | Furrow | New cell wall |

6) Why cytokinesis is important

Cytokinesis ensures:

• Each daughter cell receives its own cytoplasm
• Organelles are properly distributed
• Two cells can function independently

If cytokinesis fails:

• Cells may have multiple nuclei
• Normal growth and function are disrupted

中文（详细解释）

1）什么是细胞质分裂（Cytokinesis）

细胞质分裂是细胞分裂的最后一步，指的是细胞质被分开，形成两个独立的子细胞。

一句话： 👉 细胞质分裂 = 细胞真正分成两个

它通常发生在有丝分裂末期（末期）期间或之后。

2）细胞质分裂在细胞周期中的位置

• 间期：生长与 DNA 复制
• 有丝分裂：细胞核分裂
• 细胞质分裂：细胞整体分开

⚠️ 有丝分裂分的是“核”，细胞质分裂分的是“细胞本身”。

3）动物细胞的细胞质分裂

动物细胞通过细胞膜内陷完成分裂：

• 细胞中央形成分裂沟
• 细胞膜向内收缩
• 肌动蛋白和肌球蛋白形成收缩环
• 细胞一分为二

4）植物细胞的细胞质分裂

由于植物细胞有细胞壁，方式不同：

• 高尔基体小泡聚集在细胞中央
• 形成细胞板
• 细胞板向两侧扩展
• 形成新的细胞壁

5）动物与植物细胞的区别

| 对比项 | 动物细胞 | 植物细胞 | | ---- | ---- | ---- | | 分裂方式 | 分裂沟 | 细胞板 | | 细胞壁 | 无 | 有 | | 结果结构 | 膜内陷 | 新细胞壁 |

6）为什么细胞质分裂很重要

细胞质分裂可以：

• 让两个子细胞完全独立
• 正确分配细胞器
• 保证细胞正常生长与功能

如果细胞质分裂失败：

• 可能产生多核细胞
• 影响生物正常发育

一句话总结（双语）

• Cytokinesis = division of the cytoplasm into two cells
• 细胞质分裂 = 将一个细胞分成两个独立子细胞的过程

如果你需要，我可以继续帮你做 ✔️ cell cycle 全流程对照图（Interphase → Mitosis → Cytokinesis） ✔️ Biology 10/11 易错点清单 ✔️ 可打印或交互式标注图

Mitosis（有丝分裂）— with appropriate images

English (thorough explanation)

1) What mitosis is (core idea)

Mitosis is the process by which a cell divides its nucleus to produce two genetically identical daughter cells. It is used for growth, tissue repair, and asexual reproduction.

In simple terms: 👉 Mitosis = making two identical cells

2) Where mitosis fits in the cell cycle

• Interphase: cell grows and copies DNA (G₁, S, G₂)
• Mitosis: nucleus divides
• Cytokinesis: cytoplasm divides (often taught together with mitosis)

⚠️ DNA is not copied during mitosis—it was copied earlier in S phase.

3) The four stages of mitosis (PMAT)

Mitosis is remembered as PMAT:

P — Prophase

• Chromatin condenses into visible chromosomes
• Each chromosome has two sister chromatids
• Nuclear membrane breaks down
• Spindle fibers begin to form

M — Metaphase

• Chromosomes line up at the cell’s equator (metaphase plate)
• Spindle fibers attach to centromeres
• This alignment ensures equal separation

A — Anaphase

• Sister chromatids separate
• Pulled to opposite poles by spindle fibers
• Each chromatid is now an individual chromosome

T — Telophase

• Chromosomes reach opposite poles
• Nuclear membranes re-form
• Chromosomes decondense back into chromatin

4) Cytokinesis (often paired with mitosis)

Cytokinesis divides the cytoplasm:

• Animal cells: membrane pinches inward (cleavage furrow)
• Plant cells: a cell plate forms between the two nuclei

Result: two separate cells

5) Why mitosis is important

Mitosis allows organisms to:

• Grow (increase cell number)
• Repair damaged tissues
• Replace worn-out cells
• Reproduce asexually (in some organisms)

6) Mitosis vs meiosis (quick contrast)

| Feature | Mitosis | Meiosis | | ------------------- | --------------- | --------- | | Number of divisions | 1 | 2 | | Daughter cells | 2 | 4 | | Genetic makeup | Identical | Different | | Purpose | Growth & repair | Gametes |

中文（详细解释）

1）什么是有丝分裂（Mitosis）

有丝分裂是细胞进行细胞核分裂的过程，最终形成 两个遗传信息完全相同的子细胞。

一句话： 👉 有丝分裂 = 产生两个完全相同的细胞

2）有丝分裂在细胞周期中的位置

• 间期：细胞生长并复制 DNA
• 有丝分裂：细胞核分裂
• 细胞质分裂：细胞质分开（通常与有丝分裂一起讲）

⚠️ DNA 复制发生在间期 S 期，不是有丝分裂中。

3）有丝分裂的四个阶段（PMAT）

记忆口诀：PMAT

P — 前期（Prophase）

• 染色质凝缩成染色体
• 每条染色体由两条姐妹染色单体组成
• 核膜开始消失
• 纺锤丝形成

M — 中期（Metaphase）

• 染色体排列在细胞中央
• 纺锤丝连接着丝点
• 保证分离均等

A — 后期（Anaphase）

• 姐妹染色单体分离
• 被拉向细胞两极
• 分离后称为独立染色体

T — 末期（Telophase）

• 染色体到达两极
• 新核膜形成
• 染色体重新变成染色质

4）细胞质分裂（Cytokinesis）

• 动物细胞：细胞膜向内收缩
• 植物细胞：形成细胞板

最终形成两个独立细胞。

5）为什么有丝分裂很重要

有丝分裂使生物能够：

• 生长
• 修复组织
• 更换老化细胞
• 进行无性繁殖（部分生物）

一句话总结（双语）

• Mitosis = nuclear division producing two identical cells
• 有丝分裂 = 形成两个遗传信息相同的子细胞

如果你需要，我可以继续帮你做 ✔️ Biology 10/11 PMAT 记忆卡 ✔️ mitosis vs meiosis 对照表 ✔️ 可打印流程图或交互式动画讲解

Interphase（间期）— with appropriate images

English (thorough explanation)

1) What interphase is (core idea)

Interphase is the longest stage of the cell cycle, when a cell is not dividing but is actively growing, copying DNA, and preparing for division.

In simple terms: 👉 Interphase = preparation time before cell division

2) The three parts of interphase

Interphase has three sub-phases:

A) G₁ phase (Gap 1) — growth

• Cell grows in size
• Makes proteins and organelles
• Performs normal cell functions

B) S phase (Synthesis) — DNA replication

• DNA is copied
• Each chromosome becomes two sister chromatids
• This step is essential for accurate cell division

C) G₂ phase (Gap 2) — final preparation

• More growth
• Checks DNA for errors
• Produces materials needed for mitosis

3) What the cell looks like during interphase

• DNA is in the form of chromatin (long, thin, uncoiled)
• Chromosomes are not visible under a light microscope
• Nuclear membrane is intact
• Cell appears “normal,” but is very active internally

4) Interphase vs mitosis (common confusion)

| Feature | Interphase | Mitosis | | -------------------- | ---------------- | -------------- | | Purpose | Prepare | Divide nucleus | | DNA | Copied (S phase) | Separated | | Length | Longest | Short | | Chromosomes visible? | ❌ No | ✅ Yes |

⚠️ Interphase is part of the cell cycle but NOT part of mitosis

5) Why interphase is important

Interphase ensures:

• DNA is copied correctly
• Cell is large and ready to divide
• Daughter cells receive complete genetic information

If interphase is rushed or errors aren’t fixed, it can lead to:

• Mutations
• Cell malfunction
• Cancer

中文（详细解释）

1）什么是间期（Interphase）

间期是细胞周期中时间最长的阶段。 在这个阶段，细胞不进行分裂，而是在生长、复制 DNA，并为分裂做准备。

一句话： 👉 间期 = 细胞分裂前的准备阶段

2）间期的三个阶段

间期分为三部分：

（1）G₁ 期（生长阶段）

• 细胞体积增大
• 合成蛋白质和细胞器
• 正常进行生命活动

（2）S 期（合成阶段）

• DNA 复制
• 每条染色体复制成两条姐妹染色单体
• 为分裂做好遗传准备

（3）G₂ 期（准备阶段）

• 继续生长
• 检查 DNA 是否出错
• 合成分裂所需物质

3）间期时细胞的样子

• DNA 以染色质形式存在（细而散）
• 看不到明显染色体
• 核膜完整
• 外观看似“安静”，内部活动非常活跃

4）间期 vs 有丝分裂（考试重点）

| 对比项 | 间期 | 有丝分裂 | | ----- | -- | ---- | | 作用 | 准备 | 核分裂 | | DNA | 复制 | 分离 | | 时间 | 最长 | 较短 | | 染色体可见 | 否 | 是 |

⚠️ 间期属于细胞周期，但不属于有丝分裂

5）为什么间期很重要

间期可以：

• 确保 DNA 准确复制
• 让细胞充分生长
• 保证子细胞获得完整遗传信息

如果间期出错，可能导致：

• 基因突变
• 细胞功能异常
• 癌症

一句话总结（双语）

• Interphase = growth and DNA replication stage of the cell cycle
• 间期 = 细胞生长和 DNA 复制的准备阶段

如果你需要，我可以继续帮你做 ✔️ Biology 10/11 细胞周期速记表 ✔️ interphase vs mitosis 对比练习 ✔️ 标注版流程图或交互式 HTML 图示

Eukaryotic（真核的／真核生物的）— with appropriate images

English (thorough explanation)

1) What “eukaryotic” means (core definition)

Eukaryotic describes cells or organisms whose cells have a true nucleus and membrane-bound organelles.

In simple terms: 👉 Eukaryotic = cells with a nucleus

2) Key features of eukaryotic cells

Eukaryotic cells are characterized by:

• Nucleus

• DNA is enclosed inside a nuclear membrane

• Membrane-bound organelles, such as:

• Mitochondria (energy production)

• Endoplasmic reticulum (protein/lipid processing)
• Golgi apparatus (packaging and transport)
• Chloroplasts (plants only; photosynthesis)
• Larger and more complex than prokaryotic cells
• Linear chromosomes (DNA organized into chromosomes)

3) Types of eukaryotic organisms

All of the following are eukaryotic:

• Animals
• Plants
• Fungi
• Protists

Examples:

• Humans
• Trees
• Mushrooms
• Amoeba

They can be:

• Unicellular (e.g., many protists)
• Multicellular (plants and animals)

4) Eukaryotic vs prokaryotic (common comparison)

| Feature | Eukaryotic | Prokaryotic | | ---------- | --------------- | ----------- | | Nucleus | ✅ Present | ❌ Absent | | Organelles | ✅ Present | ❌ Absent | | Cell size | Larger | Smaller | | Complexity | High | Simple | | Examples | Animals, plants | Bacteria |

5) Why eukaryotic cells are important

Eukaryotic organization allows:

• Specialization of cells
• Multicellular life
• Complex structures and functions

Without eukaryotic cells, complex life forms (like humans) would not exist.

6) Common exam mistakes

• Thinking all unicellular organisms are prokaryotic ❌
• Forgetting that fungi are eukaryotic ❌
• Confusing nucleus with nucleoid (prokaryotes only)

中文（详细解释）

1）什么是“真核的（Eukaryotic）”

真核的指的是：细胞内具有真正细胞核，并且有膜包裹的细胞器。

一句话： 👉 真核 = 有细胞核的细胞

2）真核细胞的主要特征

真核细胞具有以下特点：

• 细胞核

• DNA 被核膜包裹

• 膜性细胞器，如：

• 线粒体（能量产生）

• 内质网
• 高尔基体
• 叶绿体（植物特有）
• 结构复杂、体积较大
• DNA 为线性染色体

3）真核生物包括哪些

以下生物全部是真核生物：

• 动物
• 植物
• 真菌
• 原生生物

它们可以是：

• 单细胞
• 多细胞

4）真核 vs 原核（考试重点）

| 项目 | 真核 | 原核 | | ---- | ----- | -- | | 细胞核 | 有 | 无 | | 细胞器 | 有 | 无 | | 复杂程度 | 高 | 低 | | 例子 | 人类、植物 | 细菌 |

5）为什么真核细胞很重要

真核细胞的结构使得：

• 细胞可以分工合作
• 生命可以进化成复杂多细胞生物

6）常见易错点

• “单细胞 = 原核” ❌
• 忽略真菌也是真核生物 ❌
• 把“拟核区”当成细胞核 ❌

一句话总结（双语）

• Eukaryotic = cells with a nucleus
• 真核的 = 有细胞核的细胞

如果你需要，我可以继续帮你做 ✔️ eukaryotic vs prokaryotic 闪卡 ✔️ Biology 10/11 常考对比题 ✔️ 标注版细胞结构练习图

Reinforcement（强化）— with appropriate images

English (thorough explanation)

1) What “reinforcement” means (core idea)

Reinforcement is anything that increases the likelihood that a behavior will happen again in the future.

In simple terms: 👉 Reinforcement = making a behavior more likely to repeat

It is a key concept in learning, psychology, education, and animal training.

2) Positive vs. negative reinforcement (very important)

Reinforcement is not the same as punishment.

A) Positive reinforcement (adding something good)

You add a pleasant stimulus after a behavior.

• Example:

• Student studies → gets praise

• Dog sits → gets a treat

➡️ Behavior increases because something good is added.

B) Negative reinforcement (removing something unpleasant)

You remove an unpleasant stimulus after a behavior.

• Example:

• Buckling a seatbelt → alarm stops

• Doing homework → nagging stops

➡️ Behavior increases because something bad is removed.

⚠️ Negative reinforcement ≠ punishment

3) Reinforcement vs punishment (common confusion)

• Reinforcement → increases behavior
• Punishment → decreases behavior

Examples:

• Giving candy for good behavior → reinforcement
• Taking away privileges for misbehavior → punishment

4) Reinforcement in learning and education

Teachers use reinforcement to:

• Encourage participation
• Build good study habits
• Shape classroom behavior

Examples:

• Verbal praise
• Stickers or points
• Extra privileges

Over time, reinforcement helps behaviors become habits.

5) Reinforcement in biology and evolution

Behaviors that:

• Improve survival
• Increase reproductive success

are naturally reinforced through natural selection.

Example:

• Animals that successfully find food repeat effective hunting behaviors.

6) Reinforcement schedules (advanced idea)

Reinforcement doesn’t always happen every time.

Common schedules:

• Continuous: every correct behavior is reinforced
• Partial / intermittent: reinforced sometimes (more resistant to extinction)

Example:

• Slot machines → unpredictable rewards → strong reinforcement

7) Why reinforcement matters

Reinforcement:

• Explains how learning occurs
• Helps shape behavior effectively
• Is used in education, therapy, parenting, and training

中文（详细解释）

1）什么是“强化（Reinforcement）”

强化是指：让某种行为在将来更容易再次发生的过程。

一句话： 👉 强化 = 增加某种行为再次出现的概率

这是心理学和学习理论中的核心概念。

2）正强化 vs 负强化（考试重点）

强化分为两种：

（1）正强化（增加好东西）

在行为之后给予奖励。

• 例子：

• 学习认真 → 得到表扬

• 小狗坐下 → 得到零食

➡️ 因为“有好处”，行为更可能重复。

（2）负强化（移除不舒服的东西）

在行为之后移除不愉快刺激。

• 例子：

• 系安全带 → 警报声消失

• 完成作业 → 不再被唠叨

➡️ 因为“不舒服的东西没了”，行为更可能重复。

⚠️ 负强化不是惩罚

3）强化 vs 惩罚（易错点）

• 强化：让行为增加
• 惩罚：让行为减少

4）教育中的强化

老师常用强化来：

• 鼓励课堂参与
• 建立良好学习习惯
• 塑造行为

常见方式：

• 表扬
• 积分
• 奖励制度

5）生物学中的强化

在自然界中：

• 有利于生存和繁殖的行为
• 更可能被重复

这是一种自然强化机制，与自然选择相关。

6）强化为什么重要

强化帮助我们理解：

• 人和动物如何学习
• 行为如何被塑造
• 为什么某些习惯难以改变

一句话总结（双语）

• Reinforcement = anything that increases a behavior
• 强化 = 让行为更容易再次发生

如果你需要，我可以继续帮你整理 ✔️ reinforcement vs punishment 对照表 ✔️ Biology / Psychology 常考情境题 ✔️ 双语闪卡（定义 + 判断练习）

Perspectives（视角／观点）— with appropriate images

English (thorough explanation)

1) What “perspectives” means (core idea)

Perspectives are the ways people see, understand, or interpret a situation, issue, or event. They are shaped by a person’s background, experiences, knowledge, culture, values, and goals.

In simple terms: 👉 Perspectives = how different people see the same thing differently

2) Why perspectives differ

People can have different perspectives because of:

• Personal experiences
• Cultural background
• Education and knowledge
• Age and generation
• Role or position (student, teacher, scientist, parent)
• Interests or values

🔹 Example: A new school policy may look helpful to teachers but stressful to students.

3) Perspectives vs opinions (important distinction)

• Perspective → a broader way of seeing shaped over time
• Opinion → a specific belief about one issue

A perspective often influences many opinions, not just one.

4) Perspectives in reading & literature

In literature, perspective often refers to:

• Point of view (first-person, third-person, omniscient)
• Narrator’s bias or limitations
• How much information the reader receives

🔹 Example: The same event feels different when told by a child versus an adult.

5) Perspectives in science & social issues

Understanding multiple perspectives helps people:

• Evaluate ethical issues
• Interpret scientific claims
• Make fair decisions

Example:

• Scientists focus on data
• Communities focus on daily impact
• Governments focus on policy and cost

All are valid perspectives, but they emphasize different concerns.

6) Why considering multiple perspectives matters

• Promotes critical thinking
• Reduces misunderstanding
• Encourages empathy
• Leads to better problem-solving

Ignoring perspectives can result in bias or unfair conclusions.

中文（详细解释）

1）什么是“Perspectives（视角 / 观点）”

Perspectives 指的是人们看待、理解和解释事物的方式。 它受到个人的经历、文化、教育、价值观和身份角色影响。

一句话： 👉 视角 = 看问题的角度

2）为什么会有不同视角

不同的人之所以有不同视角，是因为：

• 生活经历不同
• 文化背景不同
• 知识和教育不同
• 年龄和角色不同
• 价值观和关注点不同

🔹 例子： 考试制度在老师、学生和家长眼中，意义可能完全不同。

3）视角 vs 观点（易混点）

• 视角：长期形成的看问题方式
• 观点：针对某个问题的具体看法

视角往往决定一个人会形成什么观点。

4）文学中的视角

在文学作品中，视角通常指：

• 叙述视角（第一人称、第三人称等）
• 叙述者的立场和局限

不同视角会影响读者对人物和事件的理解。

5）科学与社会议题中的视角

考虑不同视角有助于：

• 理解伦理问题
• 评估科学主张
• 做出更公平的判断

例子：

• 科学家的视角关注数据
• 普通公众关注生活影响
• 政府关注成本与政策

6）为什么要理解多种视角

• 提高批判性思维
• 减少偏见
• 培养同理心
• 改善决策质量

一句话总结（双语）

• Perspectives = different ways of seeing the same situation
• 视角 = 看同一件事的不同角度

如果你需要，我可以继续帮你做 ✔️ ENGL / Socials 常考“多视角分析”模板 ✔️ perspective vs bias vs opinion 对照表 ✔️ 双语闪卡 + 情境练习

Claims（主张／论断）— with appropriate images

English (thorough explanation)

1) What a “claim” is (core idea)

A claim is a statement that asserts something is true. It is an idea or position that needs support—it is not automatically a fact.

In simple terms: 👉 Claim = what you say is true

2) Claims vs facts vs opinions

• Claim: a statement that can be supported or challenged

• Regular exercise improves concentration.

• Fact: something proven and verifiable

• Water freezes at 0°C (at standard pressure).

• Opinion: a personal belief or preference

• Exercise is fun.

A strong claim is clear, specific, and debatable.

3) Claims in arguments (very common in school)

In essays, debates, and exams, a claim is usually:

• The main point (thesis)
• Supported by evidence
• Explained by reasoning

This structure is often called CER:

• Claim
• Evidence
• Reasoning

4) Types of claims

Common categories include:

1. Claim of fact – says something is or isn’t true

2. Climate change is accelerating.

3. Claim of value – judges worth or quality

4. School uniforms are beneficial.

5. Claim of policy – suggests an action

6. Schools should start later.

5) Claims in science

In science, a claim:

• Is often based on observations or data
• Must be testable
• Can change with new evidence

Example:

• Plants grow faster under blue light than red light.

6) What makes a strong claim

A strong claim is:

• Clear (no vague language)
• Specific
• Debatable
• Supportable with evidence

Weak claim:

• Things are bad. Strong claim:
• Air pollution significantly increases asthma rates in urban children.

中文（详细解释）

1）什么是“Claims（主张 / 论断）”

Claim 指的是：一个认为某事为真的陈述。 它不是自动成立的事实，而是需要证据支持的观点。

一句话： 👉 Claim = 你提出“是真的”的观点

2）Claim、事实和观点的区别

• 主张（claim）：可以被支持或反驳
• 事实（fact）：已经被验证
• 观点（opinion）：个人看法或偏好

例子：

• Claim：阅读能提高写作能力
• Fact：一年有 365 天
• Opinion：阅读很有趣

3）写作与论证中的 claim（考试重点）

在论文和讨论中，claim 通常是：

• 中心论点（thesis）
• 需要用证据（evidence）支持
• 并用推理（reasoning）解释

常见结构： CER = Claim + Evidence + Reasoning

4）常见 claim 类型

1. 事实性主张：陈述真伪
2. 价值性主张：判断好坏
3. 政策性主张：提出行动建议

5）科学中的 claims

在科学中，claim：

• 基于数据或观察
• 必须可检验
• 会随着新证据而修正

6）什么是好的 claim

好的主张应该：

• 清楚
• 具体
• 有争议空间
• 能被证据支持

一句话总结（双语）

• Claim = a statement that needs evidence
• 主张 = 需要证据支持的论断

如果你需要，我可以继续帮你做 ✔️ CER 写作模板 ✔️ Claim vs Evidence 对比练习 ✔️ Biology / Science 论证题示例

Punnett square（潘尼特方格）— with appropriate images

English (thorough explanation)

1) What a Punnett square is (core idea)

A Punnett square is a diagram used to predict the possible genetic outcomes of a cross between two parents.

It shows:

• Which alleles parents can pass on
• All possible allele combinations in the offspring
• The probability of each genotype and phenotype

In simple terms: 👉 Punnett square = a tool to predict inherited traits

2) Why Punnett squares are used

Punnett squares help us:

• Understand inheritance patterns
• Predict offspring traits
• Calculate genetic probabilities
• Visualize dominant and recessive traits

They are widely used in Biology 9–11 and genetics problems.

3) Basic terms you must know

• Gene: a segment of DNA controlling a trait
• Allele: different versions of a gene (e.g., A or a)
• Genotype: genetic makeup (AA, Aa, aa)
• Phenotype: observable trait (tall, short)
• Dominant allele: expressed if present
• Recessive allele: expressed only if both alleles are recessive

4) How to make a simple Punnett square (monohybrid cross)

A monohybrid cross looks at one trait.

Example:

Let A = dominant, a = recessive Both parents are heterozygous (Aa)

Steps:

1. Draw a 2 × 2 grid
2. Put one parent’s alleles across the top (A, a)
3. Put the other parent’s alleles down the side (A, a)
4. Fill in the boxes by combining alleles

Results:

• AA
• Aa
• Aa
• aa

Genotype ratio: 1 AA : 2 Aa : 1 aa

Phenotype ratio: 3 dominant : 1 recessive

5) Dihybrid Punnett square (two traits)

A dihybrid cross tracks two traits at once.

• Uses a 4 × 4 grid
• Each parent produces four types of gametes
• More combinations → more variation

Example traits:

• Seed color
• Seed shape

This is more advanced but follows the same logic.

6) Probability and Punnett squares

Punnett squares show likelihood, not certainty.

Example:

• 25% chance of aa
• 50% chance of Aa
• 25% chance of AA

Each offspring is an independent event, like flipping a coin.

7) Common mistakes (exam tips)

• Mixing up genotype vs phenotype
• Forgetting that dominant ≠ common
• Writing alleles incorrectly (capital vs lowercase)
• Thinking probabilities guarantee outcomes

中文（详细解释）

1）什么是潘尼特方格（Punnett square）

潘尼特方格是一种用来预测父母杂交后代遗传结果的表格图示。

它可以显示：

• 父母可能传递的等位基因
• 后代所有可能的基因组合
• 每种结果出现的概率

一句话： 👉 潘尼特方格 = 预测遗传性状的工具

2）潘尼特方格有什么用

潘尼特方格可以帮助我们：

• 理解遗传规律
• 预测后代性状
• 计算遗传概率
• 区分显性与隐性

是中学遗传学的核心工具。

3）必须掌握的基础术语

• 基因：控制性状的 DNA 片段
• 等位基因：同一基因的不同版本
• 基因型：基因组合（AA、Aa、aa）
• 表现型：外在性状
• 显性：只要有就表现
• 隐性：必须两个都有才表现

4）单因子杂交（最常见）

单因子杂交只研究一个性状。

例子：

A = 显性 a = 隐性 父母都是 Aa

步骤：

1. 画一个 2 × 2 方格
2. 父母的等位基因分别放在上方和左侧
3. 依次填格子

结果：

• AA
• Aa
• Aa
• aa

基因型比例： 1 AA : 2 Aa : 1 aa

表现型比例： 3 显性 : 1 隐性

5）双因子杂交（进阶）

双因子杂交研究两个性状：

• 使用 4 × 4 方格
• 每个亲本产生 4 种配子
• 组合更多，变化更大

6）概率的意义

潘尼特方格显示的是概率，不是保证。

即使概率是 25%， 也不代表四个孩子一定有一个是这种性状。

7）常见考试错误

• 混淆基因型和表现型
• 认为“显性”=“更常见”（错误）
• 大小写不规范
• 把概率当作必然结果

一句话总结（双语）

• Punnett square = a tool to predict genetic outcomes
• 潘尼特方格 = 预测遗传结果的表格工具

如果你愿意，我可以下一步帮你做： ✔️ Biology 10 常考题逐步演示 ✔️ 单因子 vs 双因子对照表 ✔️ 可打印 / 可交互的 Punnett square 模板

Inherited traits（遗传性状）— with appropriate images

English (thorough explanation)

1) What “inherited traits” means

Inherited traits are characteristics passed from parents to offspring through genes. They are encoded in DNA and inherited at conception.

In simple terms: 👉 Inherited traits = traits you are born with because of your genes

2) How inherited traits are passed on

• Traits are controlled by genes
• Genes are inherited in pairs (one from each parent)
• Different versions of a gene are called alleles

The combination of alleles you receive determines how a trait is expressed.

3) Examples of inherited traits

Common inherited traits include:

• Eye color
• Natural hair color
• Blood type
• Earlobe attachment (free or attached)
• Ability to roll the tongue (often used as a teaching example)

These traits are present from birth, even if they become noticeable later.

4) Dominant and recessive traits

Some traits follow dominant–recessive inheritance:

• Dominant trait: shows if at least one dominant allele is present
• Recessive trait: shows only if both alleles are recessive

Example:

• Brown eyes (dominant)
• Blue eyes (recessive)

5) Inherited traits vs learned traits (important distinction)

• Inherited traits → passed through genes
• Learned traits → gained from environment or experience

Examples:

• Inherited: eye color, blood type
• Learned: language, skills, habits

6) Inherited traits are not always simple

Not all inherited traits follow simple dominant–recessive rules.

Some traits are:

• Polygenic (controlled by many genes, e.g., height)
• Influenced by environment (genes + lifestyle)

So genes set the potential, not always the exact outcome.

7) Why inherited traits matter

Inherited traits:

• Explain family resemblance
• Help scientists understand genetic disorders
• Are the basis of variation and evolution

中文（详细解释）

1）什么是“遗传性状”

遗传性状是指通过基因从父母传给子女的特征。 这些特征由 DNA 控制，在受精时就已经确定。

一句话： 👉 遗传性状 = 天生的、来自基因的特征

2）遗传性状如何传递

• 性状由基因控制
• 每个基因通常来自父母各一份
• 同一基因的不同版本叫做等位基因

等位基因的组合决定性状表现。

3）常见遗传性状举例

• 眼睛颜色
• 头发颜色
• 血型
• 耳垂是否分离
• 是否能卷舌（教学示例）

这些性状在出生时就已经存在。

4）显性与隐性性状

• 显性性状：只要有一个显性等位基因就会表现
• 隐性性状：只有两个隐性等位基因才会表现

例子：

• 棕色眼睛（显性）
• 蓝色眼睛（隐性）

5）遗传性状 vs 后天习得性状（考试常考）

• 遗传性状：通过基因获得
• 后天性状：通过学习或环境形成

例子：

• 遗传：血型
• 后天：语言、技能

6）遗传性状并不总是简单

很多性状是：

• 多基因控制（如身高）
• 基因 + 环境共同影响

基因决定的是可能性范围，不是绝对结果。

7）为什么遗传性状重要

遗传性状：

• 解释家庭成员的相似性
• 帮助研究遗传疾病
• 推动进化与多样性

一句话总结（双语）

• Inherited traits = traits passed from parents through genes
• 遗传性状 = 由基因决定并从父母传下来的特征

如果你需要，我可以继续帮你整理 ✔️ Biology 10 遗传章节速记卡 ✔️ 显性 / 隐性 / 多基因对照表 ✔️ 双语闪卡 + 练习题

Ethical（伦理的／道德的）— with appropriate images

English (thorough explanation)

1) What “ethical” means (core idea)

Ethical describes actions, decisions, or standards that are morally right, fair, and responsible according to accepted principles of right and wrong.

In simple terms: 👉 Ethical = doing what is right, not just what is legal or convenient

2) Ethics vs. morals (common confusion)

• Ethics → formal rules, principles, or codes (often set by professions or societies)
• Morals → personal beliefs about right and wrong

Example:

• A doctor’s ethics come from professional guidelines
• A person’s morals come from upbringing or beliefs

3) What makes an action ethical

Ethical actions usually involve:

• Fairness (no unjust advantage or harm)
• Respect (for people, rights, and dignity)
• Responsibility (considering consequences)
• Honesty (truthfulness and transparency)
• Care / non-harm (avoiding unnecessary harm)

4) Ethical decision-making (how people judge actions)

When deciding if something is ethical, people often ask:

• Who might be helped or harmed?
• Are people informed and consenting?
• Is it fair to everyone involved?
• Would it still seem right if everyone did this?

5) Ethics in science & medicine (very common in exams)

Ethics is crucial when decisions affect others’ lives.

Examples:

• Medical ethics: patient consent, privacy, end-of-life care
• Scientific research ethics: no falsifying data, protecting participants
• Genetics ethics: DNA testing, gene editing, cloning

6) Ethical vs. legal (important distinction)

• Legal → allowed by law
• Ethical → morally right

Something can be:

• Legal but unethical
• Illegal but ethically justified (in rare cases)

中文（详细解释）

1）什么是“伦理的 / 道德的（Ethical）”

ethical 指的是：行为、决定或规则符合道德原则，是公平、负责、尊重他人的。

一句话： 👉 伦理的 = 做正确的事，而不只是合法的事

2）Ethics 与 Morals 的区别（常考）

• Ethics（伦理）：社会或职业制定的规则与标准
• Morals（道德）：个人内心的对错判断

例子：

• 医生遵守的是职业伦理
• 个人遵循的是道德信念

3）什么样的行为是伦理的

通常包括：

• 公平
• 尊重他人权利与尊严
• 承担后果
• 诚实
• 不伤害他人

4）伦理判断的常见问题

判断是否符合伦理时，常问：

• 是否会对他人造成伤害或利益？
• 是否取得了知情同意？
• 是否对所有人公平？
• 如果大家都这么做，会怎样？

5）科学与医学中的伦理

伦理在涉及生命和权利时尤为重要。

例子：

• 医学伦理：病人隐私、知情同意
• 科研伦理：数据真实、保护受试者
• 基因伦理：基因检测、基因编辑

6）伦理与法律的区别

• 合法 ≠ 伦理
• 伦理关注的是“应不应该”，而不只是“可不可以”

一句话总结（双语）

• Ethical = morally right and responsible
• 伦理的 = 符合道德、公平与责任的

如果你需要，我可以继续帮你做 ✔️ ethics vs morals vs law 对照表 ✔️ Biology / Science 10 常考伦理案例 ✔️ 双语闪卡（定义＋情境判断）

Gene（基因）— with appropriate images

English (thorough explanation)

1) What a gene is (core definition)

A gene is a specific segment of DNA that contains the instructions to make a functional product—usually a protein, or sometimes a functional RNA.

In simple terms: 👉 Gene = a DNA recipe for making something useful

2) Where genes are found

• Genes are located on chromosomes
• Each gene has a specific location called a locus
• Different organisms have different numbers of genes

Example:

• Humans have ~20,000–21,000 genes

3) What genes do

Genes provide instructions for:

• Proteins (enzymes, hormones, structural proteins)
• Functional RNAs (like tRNA, rRNA)

Proteins then:

• Control chemical reactions
• Build cell structures
• Influence traits (eye color, metabolism, height potential)

4) Gene expression (how a gene works)

Genes don’t act directly. They are expressed in two main steps:

1. Transcription: DNA → mRNA
2. Translation: mRNA → protein

This process is called gene expression.

5) Genes and traits

• A trait is an observable characteristic
• Genes influence traits by controlling protein production
• The same gene can have different versions called alleles

Example:

• One gene for eye color may have multiple alleles

Traits are often affected by:

• Multiple genes
• Environmental factors

6) Mutations and genes

A mutation is a change in a gene’s DNA sequence.

• Some mutations have no effect
• Some cause changes in traits
• Some can lead to genetic disorders
• Others create variation needed for evolution

7) Gene vs DNA vs chromosome (common confusion)

• DNA → the molecule
• Gene → a functional segment of DNA
• Chromosome → a long DNA molecule with many genes

Think of it like this:

• Book = chromosome
• Chapter = gene
• Letters = DNA bases

中文（详细解释）

1）什么是“基因（Gene）”

基因是 DNA 上的一段特定序列，包含制造功能性产物（通常是蛋白质，有时是 RNA）的信息。

一句话： 👉 基因 = DNA 上的一份“功能说明书”

2）基因在哪里

• 基因位于染色体上
• 每个基因都有固定位置，称为基因座
• 不同生物的基因数量不同

例子：

• 人类大约有 2 万多个基因

3）基因的作用

基因负责指导合成：

• 蛋白质（酶、激素、结构蛋白）
• 功能性 RNA

蛋白质决定：

• 细胞如何工作
• 身体结构
• 可观察性状

4）基因如何发挥作用（基因表达）

基因通过表达来发挥功能，主要包括两步：

1. 转录：DNA → mRNA
2. 翻译：mRNA → 蛋白质

这个过程叫做 基因表达。

5）基因与性状

• 性状是可以观察到的特征
• 基因通过控制蛋白质影响性状
• 同一个基因可以有不同版本，叫 等位基因

注意：

• 多数性状由多个基因共同决定
• 环境也会影响性状表现

6）基因突变

突变是基因 DNA 序列的改变。

结果可能是：

• 没有明显影响
• 改变性状
• 引发遗传疾病
• 提供进化所需的变异

7）易混概念对比

• DNA：遗传物质
• 基因：DNA 的功能片段
• 染色体：包含许多基因的 DNA 长链

类比：

• 一本书 = 染色体
• 一章 = 基因
• 字母 = DNA 碱基

一句话总结（双语）

• Gene = a functional segment of DNA
• 基因 = DNA 上具有特定功能的一段序列

如果你需要，我可以继续帮你整理 ✔️ Biology 10/11 考点版速记表 ✔️ gene vs allele vs trait 对比 ✔️ 双语闪卡（定义 / 图示 / 易错点）

DNA（脱氧核糖核酸）— with appropriate images

English (thorough explanation)

1) What DNA is (core idea)

DNA (deoxyribonucleic acid) is the molecule that stores genetic information in almost all living organisms. It contains the instructions that tell cells how to grow, function, and reproduce.

In short: 👉 DNA = the biological instruction manual of life

2) DNA’s structure (what it looks like)

DNA has a double-helix shape—like a twisted ladder.

• Sides of the ladder: sugar–phosphate backbone
• Rungs of the ladder: pairs of nitrogenous bases

Each DNA molecule is made of many nucleotides, and each nucleotide has:

• a phosphate group
• a deoxyribose sugar
• a nitrogenous base

3) The four DNA bases & complementary pairing

DNA uses four bases:

• A = Adenine
• T = Thymine
• C = Cytosine
• G = Guanine

Complementary base pairing rules:

• A pairs with T
• C pairs with G

These pairs are held together by hydrogen bonds, which keep the structure stable but allow it to unzip when needed.

4) How DNA stores information

The sequence of bases (A, T, C, G) stores information—similar to letters forming words.

Example:

• ATGCCGTA…

Different sequences → different genes → different traits (e.g., eye color, enzymes, height potential)

5) DNA replication (copying DNA)

Before a cell divides:

1. The DNA double helix unzips
2. Each strand acts as a template
3. New complementary bases are added
4. Two identical DNA molecules are formed

This ensures genetic continuity from cell to cell.

6) DNA → traits (gene expression)

DNA itself doesn’t build structures directly. Instead:

• DNA → RNA (transcription)
• RNA → protein (translation)

Proteins then:

• Build cell structures
• Control chemical reactions
• Determine observable traits

7) Why DNA is important

DNA:

• Explains inheritance
• Allows variation and evolution
• Is used in medicine, forensics, and biotechnology

中文（详细解释）

1）什么是 DNA（核心概念）

DNA（脱氧核糖核酸）是储存遗传信息的分子，几乎存在于所有生物体中。 它包含指导细胞生长、运作和繁殖的全部信息。

一句话： 👉 DNA = 生命的说明书

2）DNA 的结构（长什么样）

DNA 呈现为双螺旋结构，就像一把扭转的梯子。

• 梯子的两边：糖–磷酸骨架
• 梯子的横档：碱基对

DNA 由大量核苷酸组成，每个核苷酸包括：

• 磷酸
• 脱氧核糖
• 含氮碱基

3）DNA 的四种碱基与互补配对

DNA 只有四种碱基：

• A（腺嘌呤）
• T（胸腺嘧啶）
• C（胞嘧啶）
• G（鸟嘌呤）

互补配对规则：

• A ↔ T
• C ↔ G

碱基之间通过氢键连接，既稳定又可分离。

4）DNA 如何储存信息

DNA 的信息由碱基排列顺序决定。

不同排列 → 不同基因 → 不同性状 （如外貌、代谢能力、身高潜力）

5）DNA 复制（细胞分裂前）

DNA 复制过程：

1. 双螺旋解开
2. 每条旧链作为模板
3. 按互补原则合成新链
4. 形成两条完全相同的 DNA

6）DNA 如何决定性状

DNA 本身不“工作”，而是通过：

• 转录：DNA → RNA
• 翻译：RNA → 蛋白质

蛋白质负责：

• 构建身体结构
• 催化反应
• 表现性状

7）DNA 为什么重要

DNA：

• 解释遗传现象
• 促进进化
• 应用于医学、法医学、生物技术

一句话总结（双语）

• DNA = the molecule that carries genetic information
• DNA = 储存并传递遗传信息的分子

如果你需要，我可以继续帮你做 ✔️ DNA → RNA → Protein 流程图 ✔️ Biology 10 / 11 考试版关键词卡 ✔️ 双语 Q/A 闪卡或交互式 HTML 图示

Organism（生物体）— with appropriate images

English (thorough explanation)

1) What “organism” means (core definition)

An organism is any individual living thing. It can be very small (like a bacterium) or very large (like a tree or a whale), but it must be able to carry out life processes on its own.

In simple terms: 👉 Organism = one living individual

2) What makes something an organism (characteristics of life)

To be considered an organism, it must show most or all of these traits:

• Made of one or more cells
• Uses energy (metabolism)
• Grows and develops
• Responds to its environment
• Maintains internal balance (homeostasis)
• Reproduces (on its own or as a species)

If something cannot perform life functions independently, it is not an organism.

3) Types of organisms

A) Unicellular organisms (one cell)

• Bacteria
• Amoeba
• Yeast

One cell performs all life functions.

B) Multicellular organisms (many cells)

• Animals
• Plants
• Most fungi

Different cells specialize, but together they form one organism.

4) Levels of organization (important concept)

In multicellular organisms, structure is organized as:

Cells → Tissues → Organs → Organ systems → Organism

🔹 Example (human):

• Muscle cell → muscle tissue → heart → circulatory system → human organism

The organism is the highest living level that functions as a complete individual.

5) Organism vs population vs species (common confusion)

• Organism → one individual (one frog)
• Population → group of the same species in one area (all frogs in a pond)
• Species → all organisms that can reproduce with each other

6) Why the concept of organism matters

• Biology studies life one organism at a time
• Health and survival depend on how an organism interacts with its habitat
• Evolution acts on populations, but selection happens to organisms

中文（详细解释）

1）什么是“生物体（Organism）”

生物体指的是单个、完整的生命个体。 它可以非常微小（如细菌），也可以非常巨大（如树或鲸鱼），但它必须能独立完成生命活动。

一句话： 👉 生物体 = 一个完整的生命个体

2）生物体必须具备的特征

一个生物体通常具有以下生命特征：

• 由一个或多个细胞构成
• 需要能量
• 能生长和发育
• 能对环境作出反应
• 能维持体内稳定（内稳态）
• 具有繁殖能力（个体或种群层面）

如果不能独立进行生命活动，就不算生物体。

3）生物体的类型

（1）单细胞生物

• 细菌
• 变形虫
• 酵母

一个细胞就能完成全部生命功能。

（2）多细胞生物

• 动物
• 植物
• 多数真菌

不同细胞分工合作，组成一个生物体。

4）结构层次（考试重点）

多细胞生物的结构层次为：

细胞 → 组织 → 器官 → 器官系统 → 生物体

🔹 人类例子： 肌肉细胞 → 肌肉组织 → 心脏 → 循环系统 → 人（生物体）

5）常见易混概念对比

• 生物体：一个个体（一只青蛙）
• 种群：同一区域的同种生物（一池塘青蛙）
• 物种：能相互繁殖的一类生物

6）为什么“生物体”很重要

• 生物学研究的基本单位
• 生物体与栖息地相互作用
• 自然选择直接作用于生物体

一句话总结（双语）

• Organism = an individual living thing
• 生物体 = 独立存在并能进行生命活动的个体

如果你愿意，我可以继续帮你做 ✔️ Biology 10 关键词对照表 ✔️ organism vs cell vs ecosystem 对比图 ✔️ 双语闪卡（定义 / 例子 / 易错点）

Stumbling（绊倒／磕磕绊绊）— with appropriate images

English (thorough explanation)

1) Literal meaning (physical)

Stumbling literally means losing balance while walking—often because your foot hits an obstacle (a rock, step, root), causing you to almost fall or take awkward steps.

• Example: He stumbled on the uneven pavement.

2) Figurative meaning (very common)

Figuratively, stumbling means having difficulty or making mistakes while trying to do something.

• Stumbling over words → speaking hesitantly or making verbal mistakes

• Stumbling through a task → progressing with errors or uncertainty

• Stumbling block → an obstacle that prevents progress

• Example: She stumbled at first, but improved with practice.

3) Grammar & forms

• Verb: stumble / stumbled / stumbling
• Noun: stumble (a mistake or misstep)
• Phrase: stumble upon → find something by accident

Examples:

• I stumbled upon an old photo. (unexpected discovery)
• The plan hit a major stumbling block.

4) Tone and nuance

• Usually mild and human, not harsh
• Often implies temporary difficulty, not failure
• Suggests learning, adjustment, or growth

Compare:

• Fail → final, strong
• Stumble → momentary, recoverable

5) Common collocations

• stumble over words / a step
• stumble through a presentation
• stumble upon an idea
• a stumbling block to success

中文（详细解释）

1）字面意思（身体动作）

stumbling 的本意是走路时被绊到、失去平衡，可能差点摔倒，但不一定真的摔倒。

• 例句：他在不平的路面上绊了一下。

2）引申意思（非常常见）

在比喻意义上，stumbling 指： 👉 做事不顺、说话卡壳、遇到困难或犯小错

常见用法：

• stumble over words → 说话结巴、卡壳

• stumble through something → 磕磕绊绊地完成

• stumbling block → 阻碍、绊脚石

• 例句：一开始他有点不顺，但慢慢就好了。

3）词形变化

• 动词：stumble / stumbled / stumbling
• 名词：stumble（失误）
• 短语：stumble upon → 偶然发现

例子：

• 我偶然发现了一张老照片。
• 这是成功路上的一个绊脚石。

4）语气与含义

• 语气 温和、人性化
• 强调 暂时的困难
• 常暗示 还能恢复、还能进步

对比：

• fail（失败） → 结果性、严重
• stumble（绊了一下） → 过程性、可调整

5）一句话总结（双语）

• Stumbling = temporary difficulty, not total failure
• stumbling = 一时不顺，而不是彻底失败

如果你愿意，我可以再补充 ✔️ ENGL/考试常见搭配表 ✔️ “stumble vs fail vs struggle” 对比 ✔️ 课堂用情境句子练习

Double helix（双螺旋）— with appropriate images

English (thorough explanation)

1) What “double helix” means

A double helix is the three-dimensional shape of DNA. It consists of two long strands that coil around each other, forming a twisted ladder.

• “Double” → two strands
• “Helix” → spiral / twisted shape

2) What the DNA double helix is made of

Each DNA strand is built from repeating units called nucleotides. Every nucleotide has:

• A phosphate group
• A deoxyribose sugar
• A nitrogenous base (A, T, C, or G)

Structure layout:

• The sugar–phosphate backbones form the outside rails of the ladder
• The bases face inward and pair up as the rungs

3) Base pairing inside the helix

Inside the double helix, bases pair complementarily:

• A pairs with T
• C pairs with G

These base pairs are held together by hydrogen bonds, while the backbone is held by strong covalent bonds.

Because of this pairing:

• The width of the helix stays constant
• Genetic information can be copied accurately

4) Why the helix twists

The ladder twists because of:

• The chemical angles of the sugar–phosphate bonds
• Interactions between stacked base pairs

This twisting:

• Makes DNA more compact
• Increases stability
• Protects genetic information

5) Major groove and minor groove

The twist creates two unequal grooves:

• Major groove → wider, more accessible
• Minor groove → narrower

These grooves are crucial because:

• Proteins (like transcription factors) bind to DNA mainly via the major groove
• This allows genes to be turned on or off

6) Why the double helix is important

The double-helix structure explains:

• DNA replication → strands separate, each serves as a template
• Mutation effects → changes in base sequence alter information
• Gene regulation → proteins recognize specific sequences via grooves

In short, the double helix is the physical basis of heredity.

中文（详细解释）

1）什么是“双螺旋”

双螺旋（double helix）是 DNA 的三维空间结构。 它由 两条长链 相互缠绕，形成一个扭曲的梯子状结构。

• 双（double） → 两条链
• 螺旋（helix） → 螺旋式缠绕

2）双螺旋的组成

DNA 的每一条链由许多 核苷酸 构成。 每个核苷酸包括：

• 磷酸
• 脱氧核糖
• 含氮碱基（A、T、C、G）

结构特点：

• 糖–磷酸骨架在外侧，形成“梯子的两边”
• 碱基在内侧，形成“梯子的横档”

3）双螺旋内部的碱基配对

碱基按照互补原则配对：

• A–T

• C–G

• 碱基之间靠 氢键连接

• 骨架内部靠 共价键连接（更牢固）

这种结构保证：

• DNA 宽度恒定
• 遗传信息稳定、可复制

4）为什么 DNA 会扭转

DNA 不保持直梯形，而是自然扭转，原因包括：

• 化学键的空间角度
• 碱基堆叠产生的相互作用

扭转的好处：

• 结构更紧凑
• 更稳定
• 更不易受损

5）大沟与小沟

双螺旋的扭转形成两种沟：

• 大沟（major groove） → 宽
• 小沟（minor groove） → 窄

它们的意义：

• 蛋白质主要通过大沟识别 DNA 序列
• 决定基因是否被表达

6）双螺旋为什么如此重要

双螺旋结构解释了：

• DNA 复制（链分开 → 各自复制）
• 突变如何影响遗传信息
• 基因调控如何发生

一句话总结： 👉 双螺旋是遗传信息储存、复制和表达的物理基础

一句话总结（双语）

• Double helix = two DNA strands twisted together
• 双螺旋 = 两条 DNA 链相互缠绕的结构

如果你需要，我可以把 double helix 做成 ✔️ Biology 10 / 11 考试版关键词卡 ✔️ “互补碱基 → 双螺旋”因果图 ✔️ 交互式 HTML 3D 旋转示意图

Habitat（栖息地）— with appropriate images

English (thorough explanation)

1) What “habitat” means (core definition)

A habitat is the natural place where an organism lives. It provides everything the organism needs to survive, grow, and reproduce, including:

• Food
• Water
• Shelter
• Space
• Suitable conditions (temperature, light, moisture)

In short: Habitat = an organism’s home in nature.

2) What makes up a habitat

A habitat includes both living (biotic) and non-living (abiotic) factors.

• Biotic factors: plants, animals, fungi, bacteria
• Abiotic factors: sunlight, temperature, water, soil, air, nutrients

🔹 Example: A pond habitat includes algae and insects (biotic) and water depth, oxygen level, and sunlight (abiotic).

3) Habitat vs. niche (important distinction)

• Habitat: Where an organism lives
• Niche: How it lives (its role, diet, interactions)

🔹 Example:

• Frog’s habitat → pond
• Frog’s niche → insect eater, prey for birds, part of the food web

Many species can share a habitat, but each has a different niche.

4) Types of habitats (common categories)

Terrestrial (land):

• Forest
• Grassland
• Desert
• Tundra

Aquatic (water):

• Freshwater (ponds, lakes, rivers)
• Marine (oceans, coral reefs)

Each habitat has specific conditions, so only organisms with suitable adaptations can live there.

5) Adaptations and habitat

Organisms have features that help them survive in their habitats.

Examples:

• Polar bear: thick fur and fat → cold Arctic habitat
• Cactus: thick stem and spines → dry desert habitat
• Fish: gills → aquatic habitat

If conditions change too much, the organism may struggle or die.

6) Why habitats matter

• Support biodiversity
• Maintain food webs
• Provide ecosystem services (clean water, oxygen, soil stability)

Habitat destruction (deforestation, pollution, urbanization) is one of the biggest threats to species survival.

中文（详细解释）

1）什么是“栖息地（Habitat）”

栖息地是指生物自然生活的地方。 它为生物提供生存所需的一切条件，包括：

• 食物
• 水
• 庇护所
• 活动空间
• 合适的环境条件（温度、光照、湿度等）

一句话： 👉 栖息地 = 生物在自然界中的“家”

2）栖息地的组成

栖息地由生物因素和非生物因素共同构成。

• 生物因素： 植物、动物、真菌、细菌
• 非生物因素： 阳光、温度、水、空气、土壤、养分

🔹 例子： 池塘栖息地不仅有鱼和水草，还有水温、含氧量和光照条件。

3）栖息地 vs 生态位（考试常考）

• 栖息地： 生物住在哪里
• 生态位： 生物如何生存、扮演什么角色

🔹 例子：

• 青蛙的栖息地 → 池塘
• 青蛙的生态位 → 捕食昆虫、被鸟类捕食

4）常见栖息地类型

陆地栖息地：

• 森林
• 草原
• 沙漠
• 苔原

水生栖息地：

• 淡水（湖泊、河流、池塘）
• 海洋（海洋、珊瑚礁）

每种栖息地都有独特环境条件。

5）栖息地与适应

生物具有适应其栖息地的特征。

例子：

• 北极熊：厚毛和脂肪 → 寒冷地区
• 仙人掌：肉质茎和刺 → 干旱沙漠
• 鱼类：鳃 → 水生环境

环境变化过大，生物可能无法生存。

6）为什么栖息地很重要

• 维持生物多样性
• 支撑食物网
• 提供生态系统服务

栖息地破坏是物种灭绝的重要原因之一。

一句话总结（双语）

• Habitat = where an organism lives
• 栖息地 = 生物生活的自然环境

如果你需要，我可以把 habitat 整理成 ✔️ 双语闪卡（定义 / 对比 / 易错点） ✔️ Habitat vs niche 对照表 ✔️ 适合 Biology 10 的练习题与图片标注

Unity（统一性）— with appropriate images

English (thorough explanation)

1) What “unity” means (core idea)

Unity means everything works together as a whole. Different parts may vary, but they feel connected, consistent, and purposeful, not random or chaotic.

Unity answers the question: 👉 “Do all parts belong together?”

2) Unity in art & design (most common use)

In art, design, and visual composition, unity refers to how elements combine to create a cohesive visual experience.

Unity is achieved through:

• Repetition (same colors, shapes, fonts)
• Consistency (style, spacing, alignment)
• Proximity (related items placed close together)
• Alignment (elements line up logically)
• Harmony (elements complement rather than clash)

🔹 Example: A poster using one color palette, one font family, and repeated shapes feels unified.

Unity ≠ sameness Unity allows variety, but within a shared structure.

3) Unity vs. variety (important distinction)

• Unity = togetherness
• Variety = differences that add interest

Good design balances both:

• Too much unity → boring
• Too much variety → chaotic

🔹 Think of a song: Different notes and rhythms, but one key and mood.

4) Unity in biology

In biology, unity refers to how different parts function together to support life.

Examples:

• An organism: organs → systems → whole body
• An ecosystem: producers, consumers, decomposers working together
• Unity of life: all living things share DNA, cells, and basic biochemical processes

🔹 Example: Heart, lungs, and blood vessels are different, but form one circulatory system.

5) Unity in chemistry

In chemistry, unity describes how atoms bond to form a stable molecule.

Examples:

• Individual atoms are meaningless alone
• Together, they form compounds with new properties (e.g., H₂O)

Unity here means:

• Fixed ratios
• Predictable structure
• Shared electron systems

6) Unity in writing & thinking

In writing or arguments, unity means:

• Every paragraph supports one central idea
• No irrelevant details
• Clear logical flow

A unified essay:

• One thesis
• All evidence connects back to it

中文（详细解释）

1）什么是“统一性（Unity）”

统一性指的是：各个部分共同组成一个整体。 虽然每个部分可能不同，但它们之间相互联系、协调一致。

统一性回答的问题是： 👉 “这些部分是否属于同一个整体？”

2）艺术与设计中的统一性

在艺术、平面设计、网页设计中，统一性指画面是否整体协调、不杂乱。

实现统一性的方式包括：

• 重复（颜色、形状、字体）
• 一致性（风格、大小、间距）
• 接近性（相关元素靠近）
• 对齐（有清晰的排列逻辑）
• 和谐（不冲突）

🔹 例子： 一个网站如果颜色、按钮样式、字体统一，看起来就专业、清晰。

3）统一性 vs 多样性（考试常考）

• 统一性 → 整体感
• 多样性 → 变化与趣味

好的作品需要二者平衡：

• 只有统一 → 单调
• 只有变化 → 混乱

4）生物学中的统一性

在生物学中，统一性强调不同结构协同运作。

例子：

• 器官 → 系统 → 个体
• 生态系统中的不同物种相互依存
• 生命的统一性：所有生物都有细胞、DNA、相似代谢过程

🔹 例子： 心脏、肺、血管功能不同，但共同维持生命。

5）化学中的统一性

在化学中，统一性体现在：

• 原子通过化学键形成稳定整体
• 形成的新物质具有整体性质

🔹 例子： 氢和氧单独存在与结合成水，性质完全不同。

6）写作与思维中的统一性

在写作中，统一性意味着：

• 所有段落服务于同一个中心思想
• 没有跑题内容
• 逻辑清晰、层次分明

一句话总结（双语）

• Unity = many parts, one whole
• 统一性 = 多个部分，构成一个整体

如果你愿意，我可以把 unity 做成 ✔️ 考试用关键词对照表 ✔️ 艺术 / 生物 / 化学对比图 ✔️ 双语闪卡（定义 + 例子 + 易错点）

Reviewer #1 (Public review):

Summary:

Syed et al. investigate the circuit underpinnings for leg grooming in the fruit fly. They identify two populations of local interneurons in the right front leg neuromere of ventral nerve cord, i.e. 62 13A neurons and 64 13B neurons. Hierarchical clustering analysis identifies each 10 morphological classes for both populations. Connectome analysis reveals their circuit interactions: these GABAergic interneurons provide synaptic inhibition either between the two subpopulations, i.e. 13B onto 13A, or among each other, i.e. 13As onto other 13As, and/or onto leg motoneurons, i.e. 13As and 13Bs onto leg motoneurons. Interestingly, 13A interneurons fall into two categories with one providing inhibition onto a broad group of motoneurons, being called "generalists", while others project to few motoneurons only, being called "specialists". Optogenetic activation and silencing of both subsets strongly effects leg grooming. As well activating or silencing subpopulations, i.e. 3 to 6 elements of the 13A and 13B groups has marked effects on leg grooming, including frequency and joint positions and even interrupting leg grooming. The authors present a computational model with the four circuit motifs found, i.e. feed-forward inhibition, disinhibition, reciprocal inhibition and redundant inhibition. This model can reproduce relevant aspects of the grooming behavior.

Strengths:

The authors succeeded in providing evidence for neural circuits interacting by means of synaptic inhibition to play an important role in the generation of a fast rhythmic insect motor behavior, i.e. grooming of the body using legs. Two populations of local interneurons in the fruit fly VNC comprise four inhibitory circuit motifs of neural action and interaction: feed-forward inhibition, disinhibition, reciprocal inhibition and redundant inhibition. Connectome analysis identifies the similarities and differences between individual members of the two interneuron populations. Modulating the activity of small subsets of these interneuron populations markedly affects generation of grooming behavior thereby exemplifying their relevance. The authors carefully discuss strengths and limitations of their approaches and place their findings into the broader context of motor control.

Weaknesses:

Effects of modulating activity in the interneuron populations by means of optogenetics were conducted in the so-called "closed-loop" condition. This does not allow to differentiate between direct and secondary effects of the experimental modification in neural activity, as feedforward and feedback effects cannot be disentangled. To do so open loop experiments, e.g. in deafferented conditions, would be needed. Given that many members of the two populations of interneurons do not show one, but two or more circuit motifs, it remains to be disentangled which role the individual circuit motif plays in the generation of the motor behavior in intact animals.

Comments on revisions:

The authors have carefully revised the manuscript. I have no further suggestions or criticisms.

Reviewer #3 (Public review):

Summary:

The authors set out to determine how GABAergic inhibitory premotor circuits contribute to the rhythmic alternation of leg flexion and extension during Drosophila grooming. To do this, they first mapped the ~120 13A and 13B hemilineage inhibitory neurons in the prothoracic segment of the VNC and clustered them by morphology and synaptic partners. They then tested the contribution of these cells to flexion and extension using optogenetic activation and inhibition and kinematic analyses of limb joints. Finally, they produced a computational model representing an abstract version of the circuit to determine how the connectivity identified in EM might relate to functional output. The study makes important contributions to the literature.

The authors have identified an interesting question and use a strong set of complementary tools to address it:

They analysed serial‐section TEM data to obtain reconstructions of every 13A and 13B neuron in the prothoracic segment. They manually proofread over 60 13A neurons and 64 13B neurons, then used automated synapse detection to build detailed connectivity maps and cluster neurons into functional motifs.

They used optogenetic tools with a range of genetic driver lines in freely behaving flies to test the contribution of subsets of 13A and 13B neurons.

They used a connectome-constrained computational model to determine how the mapped connectivity relates to the rhythmic output of the behavior.

Comments on revisions:

I appreciate that the authors have updated the GitHub repository to include the model and analysis code. Still lacking is: for the authors to explicitly separate empirical findings from modelling inferences in the text, and a supplemental table to make it clear which cell types are included. I should also point out that the code lacks annotations necessary for the results to be reproduced and the model to be reused.

Author response:

The following is the authors’ response to the previous reviews.

Public Reviews:

Reviewer #1 (Public review):

Summary:

Syed et al. investigate the circuit underpinnings for leg grooming in the fruit fly. They identify two populations of local interneurons in the right front leg neuromere of ventral nerve cord, i.e. 62 13A neurons and 64 13B neurons. Hierarchical clustering analysis identifies each 10 morphological classes for both populations. Connectome analysis reveals their circuit interactions: these GABAergic interneurons provide synaptic inhibition either between the two subpopulations, i.e. 13B onto 13A, or among each other, i.e. 13As onto other 13As, and/or onto leg motoneurons, i.e. 13As and 13Bs onto leg motoneurons. Interestingly, 13A interneurons fall into two categories with one providing inhibition onto a broad group of motoneurons, being called "generalists", while others project to few motoneurons only, being called "specialists". Optogenetic activation and silencing of both subsets strongly effects leg grooming. As well activating or silencing subpopulations, i.e. 3 to 6 elements of the 13A and 13B groups has marked effects on leg grooming, including frequency and joint positions and even interrupting leg grooming. The authors present a computational model with the four circuit motifs found, i.e. feed-forward inhibition, disinhibition, reciprocal inhibition and redundant inhibition. This model can reproduce relevant aspects of the grooming behavior.

Strengths:

The authors succeeded in providing evidence for neural circuits interacting by means of synaptic inhibition to play an important role in the generation of a fast rhythmic insect motor behavior, i.e. grooming. Two populations of local interneurons in the fruit fly VNC comprise four inhibitory circuit motifs of neural action and interaction: feed-forward inhibition, disinhibition, reciprocal inhibition and redundant inhibition. Connectome analysis identifies the similarities and differences between individual members of the two interneuron populations. Modulating the activity of small subsets of these interneuron populations markedly affects generation of the motor behavior thereby exemplifying their important role for generating grooming. The authors carefully discuss strengths and limitations of their approaches and place their findings into the broader context of motor control.

We thank the reviewer for their thoughtful and constructive evaluation of our work.

Weaknesses:

Effects of modulating activity in the interneuron populations by means of optogenetics were conducted in the so-called closed-loop condition. This does not allow to differentiate between direct and secondary effects of the experimental modification in neural activity, as feedforward and feedback effects cannot be disentangled. To do so open loop experiments, e.g. in deafferented conditions, would be important. Given that many members of the two populations of interneurons do not show one, but two or more circuit motifs, it remains to be disentangled which role the individual circuit motif plays in the generation of the motor behavior in intact animals.

Our optogenetic experiments show a role for 13A/B neurons in grooming leg movements – in an intact sensorimotor system - but we cannot yet differentiate between central and reafferent contributions. Activation of 13As or 13Bs disinhibits motor neurons and that is sufficient to induce walking/grooming. Therefore, we can show a role for the disinhibition motif.

Proprioceptive feedback from leg movements could certainly affect the function of these reciprocal inhibition circuits. Given the synapses we observe between leg proprioceptors and 13A neurons, we think this is likely.

Our previous work (Ravbar et al 2021) showed that grooming rhythms in dusted flies persist when sensory feedback is reduced, indicating that central control is possible. In those experiments, we used dust to stimulate grooming and optogenetic manipulation to broadly silence sensory feedback. We cannot do the same here because we do not yet have reagents to separately activate sparse subsets of inhibitory neurons while silencing specific proprioceptive neurons. More importantly, globally silencing proprioceptors would produce pleiotropic effects and severely impair baseline coordination, making it difficult to distinguish whether observed changes reflect disrupted rhythm generation or secondary consequences of impaired sensory input. Therefore, the reviewer is correct – we do not know whether the effects we observe are feedforward (central), feedback sensory, or both. We have included this in the revised results and discussion section to describe these possibilities and the limits of our current findings.

Additionally, we have used a computational model to test the role of each motif separately and we show that in the results.  

Comments on revisions:

The careful revision of the manuscript improved the clarity of presentation substantially.

Reviewer #2 (Public review):

Summary:

This manuscript by Syed et al. presents a detailed investigation of inhibitory interneurons, specifically from the 13A and 13B hemilineages, which contribute to the generation of rhythmic leg movements underlying grooming behavior in Drosophila. After performing a detailed connectomic analysis, which offers novel insights into the organization of premotor inhibitory circuits, the authors build on this anatomical framework by performing optogenetic perturbation experiments to functionally test predictions derived from the connectome. Finally, they integrate these findings into a computational model that links anatomical connectivity with behavior, offering a systems-level view of how inhibitory circuits may contribute to grooming pattern generation.

Strengths:

(1) Performing an extensive and detailed connectomic analysis, which offers novel insights into the organization of premotor inhibitory circuits.

(2) Making sense of the largely uncharacterized 13A/13B nerve cord circuitry by combining connectomics and optogenetics is very impressive and will lay the foundation for future experiments in this field.

(3) Testing the predictions from experiments using a simplified and elegant model.

Thank you for the positive assessment of our work.

Weaknesses:

(1) In Figure 4-figure supplement 1, the inclusion of walking assays in dusted flies is problematic, as these flies are already strongly biased toward grooming behavior and rarely walk. To assess how 13A neuron activation influences walking, such experiments should be conducted in undusted flies under baseline locomotor conditions.

We agree that there are better ways to assay potential contributions of 13A/13B neurons to walking. We intended to focus on how normal activity in these inhibitory neurons affects coordination during grooming, and we included walking because we observed it in our optogenetic experiments and because it also involves rhythmic leg movements. The walking data is reported in a supplementary figure because we think this merits further study with assays designed to quantify walking specifically. We will make these goals clearer in the revised manuscript and we are happy to share our reagents with other research groups more equipped to analyze walking differences.

(2) Regarding Fig 5: The 70ms on/off stimulation with a slow opsin seems problematic. CsChrimson off kinetics are slow and unlikely to cause actual activity changes in the desired neurons with the temporal precision the authors are suggesting they get. Regardless, it is amazing the authors get the behavior! It would still be important for authors to mention the optogentics caveat, and potentially supplement the data with stimulation at different frequencies, or using faster opsins like ChrimsonR.

We were also intrigued by the behavioral consequences of activating these inhibitory neurons with CsChrimson. We appreciate the reviewer’s point that CsChrimson’s slow off-kinetics limit precise temporal control. To address this, we repeated our frequency analysis using a range of pulse durations (10/10, 50/50, 70/70, 110/110, and 120/120 ms on/off) and compared the mean frequency of proximal joint extension/flexion cycles across conditions. We found no significant difference in frequency (LLMS, p > 0.05), suggesting that the observed grooming rhythm is not dictated by pulse period but instead reflects an intrinsic property of the premotor circuit once activated. We now include these results in ‘Figure 5—figure supplement 1’ and clarify in the text that we interpret pulsed activation as triggering, rather than precisely pacing, the endogenous grooming rhythm. We continue to note in the manuscript that CsChrimson’s slow off-kinetics may limit temporal precision. We will try ChrimsonR in future experiments.

Overall, I think the strengths outweigh the weaknesses, and I consider this a timely and comprehensive addition to the field.

Reviewer #3 (Public review):

Summary:

The authors set out to determine how GABAergic inhibitory premotor circuits contribute to the rhythmic alternation of leg flexion and extension during Drosophila grooming. To do this, they first mapped the ~120 13A and 13B hemilineage inhibitory neurons in the prothoracic segment of the VNC and clustered them by morphology and synaptic partners. They then tested the contribution of these cells to flexion and extension using optogenetic activation and inhibition and kinematic analyses of limb joints. Finally, they produced a computational model representing an abstract version of the circuit to determine how the connectivity identified in EM might relate to functional output. The study makes important contributions to the literature.

The authors have identified an interesting question and use a strong set of complementary tools to address it:

They analysed serial‐section TEM data to obtain reconstructions of every 13A and 13B neuron in the prothoracic segment. They manually proofread over 60 13A neurons and 64 13B neurons, then used automated synapse detection to build detailed connectivity maps and cluster neurons into functional motifs.

They used optogenetic tools with a range of genetic driver lines in freely behaving flies to test the contribution of subsets of 13A and 13B neurons.

They used a connectome-constrained computational model to determine how the mapped connectivity relates to the rhythmic output of the behavior.

Recommendations for the authors:

Reviewer #1 (Recommendations for the authors):

I still have the following specific suggestions and questions, which need the attention of the authors:

P5, 2nd para, li 1: shouldn't "(Figures 1E and 1E')" be (Figures 1G and 1H)?

P7, last para, li 3: shouldn't "(Figures 2C and 2D)" be (Figures 2A and 2B)?

P19, para 2, last 2li: "...we observe that optogenetic activation......triggers grooming movements." I could not find the place in the text or a figure, where this was reported or shown. Please specify

P19, last para: "... shows that 13A neurons can generate rhyhtmic movements....." Given that the experiments were conducted in closed-loop, i.e. including the loop through the leg and its movements, the following formulation appears more justified: "....shows that 13A neurons significantly contribute to the generation of rhythmic movements,....."

P28, para 1, li 3 from bottom: "...themselves, rather than solely between antagonistsic motor neurons." While the authors are correct that in the stick insect and locust alternating inhibitory synaptic drive to flexor and extensor motoneurons has been shown to underly alternating activity of these two antagonistic motoneuron pools the previous studies have not shown or claimed that these synaptic inputs arise from direct interactions between these motoneuron pools. Based on this this text should be moved to the part "feed-forward inhibition" on page 27.

P28: "redundant inhibition": this motif has been shown to be instrumental in the locust flight CPG, e.g. Robertson & Pearson, 1985, Fig. 16.

P28: "reciprocal inhibition" The reviewer agrees with the authors that this motif has been shown for the mouse spinal cord, but also for other CPGs in vertebrates and invertebrates, e.g. clione, leech, xenopus - see the initial comment "(3) Intro and Discussion"

Thank you, we have incorporated the suggested corrections and clarifications into the revised manuscript.

Reviewer #2 (Recommendations for the authors):

I'm satisfied with the revised version

Reviewer #3 (Recommendations for the authors):

The authors have made a substantial effort to address my original points. They corrected the title, expanded Discussion and Methods sections, reran statistical tests using mixed models, added modelling clarifications and constraints, and fixed or removed confusing figure panels. Those changes have improved clarity and reduced some of the claims that I thought were exaggerated.

That said, some of my concerns remain only partially addressed, which could be fixed with relatively small tweaks. The authors should:

(1) Explicitly separate empirical findings from modelling inferences throughout the manuscript, including the Abstract, Results and Discussion (i.e., label claims of "intrinsic rhythmogenesis" as model-based inferences, not direct experimental demonstrations)

(2) Provide supplemental information on modelling to quantify the role of the black-box input (e.g., quantitative coordination/phase/frequency metrics for full model vs constant-input vs no black box), show pre- vs post-fine-tuning weight changes and the exact tuning constraints/optimization details (I could not find these details)

(3) To ensure results are reproducible, provide a supplemental table mapping each split line to EM-identified neuron(s) with NBLAST/morphological scores for each match;

(4) Fully document the statistical models (exact LMM/GLMM formulas, software/packages, etc);

(5) Deposit model code, trained weights and analysis scripts in a public repository.

We have updated the GitHub repository with the full statistical analysis documentation and model code, including trained weights and scripts.

"lower extremity?"

"lower extremity?"

Perhaps use "upper extremity" to avoid reinforcing the perception of "arm" as referring to the entire upper extremity.

Should we mention earlier that the cord ends at L1?

I would like to see us tie this back to the conversation about the role of oxygen in ATP production to reinforce why we die without oxygen.

I'm not sure why we are omitting the coccygeal region here.

Do we want to emphasize the point here that respiration is not primarily controlled by oxygen levels?

Maybe we also mention their role in synapse formation?

We clarified olfactory epithelium here, but not retina. We might want to clarify both as we have not defined retina yet and some students may be unfamiliar with the term.

As we have not yet defined neuroglia, students may misinterpret this as a substance, not a cell type. Maybe "made by cells that support the nervous system called glial cellls, which we will explore in more detail later."