5,190 Matching Annotations
  1. Jun 2019
    1. trophic cascades

      Also known as top-down controls, these refer to the effects of predators that propagate downward through food webs across multiple trophic levels—where trophic level refers to an organism's position in the food chain.

    1. zona incerta (ZI)

      A part of the brain.

      The function of this area is poorly understood but is thought to regulate behavior of an animal in response to internal (such as hunger) and external (such as pain) sensory cues.

    2. γ-aminobutyric acid (GABA)

      An inhibitory neurotransmitter. Neurons communicate with each other by releasing neurotransmitters. Neurons respond to inhibitory neurotransmitters by reducing their activity.

    3. type A GABA (GABAA) receptor antagonist bicuculline (Bic)

      A light-sensitive competitive agonist of GABA<sub>A</sub> receptors. It was originally isolated and identified over 40 years ago in the Dicentra cucullaria plant.

    1. Parkinson's disease

      A progressive degenerative disorder primarily impacting motor control that can lead to tremors or stiffness. Pathologically characterized by the loss of dopamine-secreting neurons in two parts of the brain (the substantia nigra pars compacta and basal ganglia), as well as the presence of Lewy bodies—aggregates of a protein called alpha synuclein contained within the neuron.

  2. May 2019
    1. cytokines

      Cytokines are proteins that are released by immune cells to activate the immune response in other cells.

      Example: When a cell is infected with a virus, it can release the cytokine interferon to signal neighboring cells of an incoming viral attack. This allows the neighboring cells to increase production of anti-viral proteins.

    2. prototypic

      Prototypic means the original model in which further knowledge is based off of.

      Since acetylcholine was the first neurotransmitter discovered, its function/ behavior is what all other neurotransmitters are based off of.

    3. T cell

      A T cell is a type of immune cell responsible for directing the adaptive immune system's response to infection, allergy and cancer.

      • note: think of the T cell as a general of an army.
    1. catalysis

      Catalysis is the initiation and acceleration of a chemical reaction.

      In this case, the authors point to KDM6B as the catalyst for Dmrt1 expression and thus male sex development.

    1. will stand for no amino acid—that is, will be nonsense

      As a general rule, there are four kinds of codons: codons that initiate the reading frame, codons that stop the reading frame, codons that code for amino acids to make proteins, and codons that don't code for anything at all (called nonsense codons).

    2. Deductions

      Crick relies on deductive reasoning to make his argument for the nature of the genetic code.

      Deductive reasoning draws specific conclusions from general principles or premises, whereas inductive reasoning infers general principles from specific instances.

    3. 2',3' hydroxyls on the sugar.

      Hydroxyls are -OH groups and are found on the sugar ribose on the second and third carbon. In RNA, only one chemical unit in the entire strand has a hydroxyl on both the second and third (2' and 3') carbon.

      Check out this image to identify the hydroxyls found on second and third carbon.

    4. "right-hand" end

      Just as your left and right hands are distinct mirror images, certain molecules have distinct mirror images, too. When a molecule has a distinct mirror image, we say the molecule is chiral.

      All sugars in the body are "right handed." On a strand of genetic material, the sugars are linked together such that only one end of the chain is "handed."

    5. poly (U,C)

      Crick defines poly(Y, Z) as a DNA strand with equal amounts of two bases "Y" and "Z" in random order. Here, poly(U, C) is then a strand of genetic material with equal amounts of uracil and cytosine in random order.

    6. acridines

      An organic molecule that is not naturally found in cells, as they are substituted derivatives of the parent ring.

      Acridines were previously used in some dyes and many have antiseptic properties, but usage largely stopped since acridines are also a skin irritant.

    7. bacteriophage T4

      A bacteriophage is a type of virus that infects bacteria. The T4 bacteriophage is a specific bacteriophage that infects E coli. Bacteriophages—like all living organisms—have genetic material.

    8. A and B cistrons

      A section of DNA or RNA that codes for a specific chain of amino acids, or "polypeptide chain." Cistron is synonymous with gene, meaning A and B cistrons are two different genes. The term cistron has largely fallen out of favor.

    9. the amino end

      Imagine kids lined up holding hands: The line leader will have no one to hold her left hand and the caboose will have no one to hold her right hand.

      Amino acids on a protein have a similar feature. The first amino acid will have an amine group exposed and the last amino acid will have an acid group exposed. The "amino end" refers to the end of the strand where the amine group is exposed.

    10. Gamow's

      George Gamow (1904–1968) was a theoretical physicist. Curious about the natural world, he was often in contact with scientific giants outside of physics, such as Crick. Despite his inexperience in chemistry and biology, Gamow learned about these fields and ultimately influenced their progress. Gamow is just one of many historical examples of an outside, non-expert perspective having a profound influence on a difficult problem.

    11. genetic recombination

      The exchange of genetic material between two different organisms. In the case of T4 bacteriophage, this is done by infecting a single E. coli cell with multiple phages. The phage genomes then recombine and produce new variants.

    12. messenger RNA

      A class of RNA that acts as a messenger of genetic information, delivering the code from DNA to a ribosome where it is translated into amino acids, eventually resulting in a polypeptide or protein.

    13. a sequence of 20 or more things is determined by a sequence of four things of a different type.

      That is, a specific sequence of bases encodes a specific sequence of amino acids. Within this code, which is used by all living organisms, there are only four kinds of bases and 20 kinds of amino acids.

    14. bases

      Here, bases refer to the chemical pendants—side groups of molecules—that are found on the backbone of nucleotides. Nucleotides consist of a sugar called deoxyribose, a phosphate group, and one of five bases.

      An example of a base is guanine.

    1. moderation effect

      Moderating variables are variables that affect the direction of strength of a relationship between dependent and independent variables (in this case, the level of endorsement of stereotype threat is the moderating variable).

      A moderating effect is the result of the influence of a moderating variable.

    2. main

      A main effect is the effect of one independent variable (in this case gender) on the dependent variable (in this case beginning-of-semester FMCE scores), and ignores the effects of other independent variables.

    1. fidelity

      How specifically an enzyme carries out its function. We can say that Cas13b has high fidelity because it produced very few off-targets in the knockdown experiment (see Figures 1E, 1F, and 1G).

    2. structure-guided protein engineering

      When researchers want to modify a protein to improve a particular feature, they can use the knowledge of the protein's 3D structure to identify and modify key amino acids in the sequence.

    3. coverage

      When you sequence a genome, you do it in pieces rather than in a single, continuous stretch. This is similar to cutting the genome up and then putting it back together again, like a puzzle. Each base may be read multiple times and be a part of multiple sequences—comparing pieces to see where they overlap is how the full genome is reconstructed. The number of times a base is read is called the "coverage," and higher coverage leads to a more accurate sequence.

    4. adeno-associated viral (AAV) vectors

      Adeno-associated virus (AAV) is a human virus that is present in 80% - 90% of the adult population but does not cause any disease. This virus has been extensively used as a biomolecular tool because it is small and has low risk of genome integration and causing unwanted mutations.

    5. the ClinVar database

      ClinVar is an archive that collects data about the relationship between gene variants and phenotypes. It contains more than 400,000 records.

      ClinVar is free to use—try looking up information about AVPR2. Search for AVPR2 to find out more about the 878G>A mutation that the authors looked at.

    6. Fanconi anemia

      Fanconi anemia (FA) is a rare genetic condition resulted from nonfunctional DNA repair mechanisms.

      Because DNA repair is vital for every cell in the body, all organs are affected when repair mechanisms don't function properly. Organs that contain frequently dividing cells (such as skin) are the most affected. People with Fanconi anemia have bone marrow defects, organ abnormalities, and an increased risk of some cancers.

    7. FANCC

      FANCC codes for a protein involved in the Fanconi anemia (FA) disease pathway.

      This pathway is activated when the cell DNA gets damaged. The FANCC protein is a part of a complex responsible for recognizing this DNA damage and activating repair mechanisms.

    8. PPIB

      Stands for, Peptidylprolyl Isomerase B (also known as Cyclophilin B), which codes for a protein that regulates protein folding in the cytoplasmic reticulum. Some mutations of PPIB result in impaired bone development.

    9. DNA base editors, consisting of a fusion between Cas9 nickase and cytidine deaminase, can mediate efficient cytidine-to-uridine conversions within a target window and substantially reduce the formation of double-strand break–induced indels

      DNA base editing is a technique which allows precise conversion of one nucleotide into another without any template sequence.

      A base editor is a fusion protein made up of a protein that recognizes specific DNA sequences (for example, Cas9), and a deaminase that can convert one amino acid to another (i.e., cytidine [C] to uridine [U] or adenosine [A] to inosine [I]).

      Because of the geometry of the proteins, this conversion can only happen in a certain range of nucleotides, called the target window.

    10. frame shifts

      Genes are transcribed into proteins by codons, which are made up of sequences of three amino acids. Mutations that occur in numbers divisible by three will not affect the reading frame, but those not divisible by three will cause a shift in the reading frame. Generally, a mutation in-frame will not disrupt the protein function and can be handled by the cell. A frame-shift mutation will completely inactivate a protein and can be very detrimental to cellular function in some cases.

      For example:

      Original sequence: THE CAT WAS RED

      Frame shift mutation: ATH ECA TWA SRE D

      Non-frame shift mutation: THE BIG CAT WAS RED

    11. Cpf1

      Cpf1 is a nuclease that is analogous to Cas9.

      Cpf1 differs from Cas9 in a number of ways. The most important one is that when Cpf1 cuts DNA, it leaves overhangs. It also requires different PAM sequences, which are short sequences that help the system distinguish self DNA from non-self DNA.

      Cfp1 has the potential to be more accurate than Cas9, and can sometimes be used when there are no sequences that Cas9 can use as a target.

    12. Precise nucleic acid–editing technologies

      These techniques allow researchers to modify a chosen nucleic acid sequence.

      The most widely used technologies are TALENs (transcription activator-like effector nucleases), ZFNs (zinc finger nucleases) and CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/CRISPR associated protein 9).

      CRISPR is the most popular since it can be programmed to new sequences using a guide RNA, whereas other tools must be engineered at the protein level, which is difficult and time consuming. The focus of this paper is a variation of CRISPR that uses Cas13.

  3. Apr 2019
    1. character displacement

      When two competing species overlap in habitat, natural selection may drive one population to use resources that are not used by individuals of the other population. This allows two similar species to coexist.

    1. solar absorptance of 0.91

      The fraction of the sun radiation that penetrates the surface. A solar absorptance of 0.91 means that 91% of the sun's radiation penetrates the material and is converted to heat.

    2. face-centered cubic topology

      Describes the 3D geometry of the MOF. MOF-801 is constituted of a repetition of cubes having one cluster in each corner and each center of the faces. Figure 1B shows one of these small cubes constituting the repeating unit of the MOF.

    3. porosity

      The ratio of the cavities' volume to the total volume of the material. MOFs are made of microscopic crystals, which are responsible for the presence of these cavities. Porosity can range from 0 to 1, a porosity of 0 meaning that there are no cavities within the structure.

    4. 1 sun

      Unit of light intensity corresponding to 1000 watts per square meter. For reference, if you stood one meter away from a standard 60-watt light bulb, the light intensity would be equal to about 4.8 watts per square meter.

    5. [Zr6O4(OH)4(fumarate)6]

      The chemical composition of MOF-801. This specific MOF is based on zirconium (Zr) metal ions linked together by fumarate molecules, which are small organic compounds made of carbon, oxygen, and hydrogen.

    1. superlubricity

      The state of near-zero friction at the sliding interfaces of two contacting solid surfaces is called superlubricity. In superlubric regimes, the extent of physical and/or chemical interactions is extremely small and hence the surfaces can slide over one another without causing much friction.

    1. heritability

      A statistic that describes how much variation of a specific trait can be attributed to genetics. With these finches, it's a measure of how well differences in beak genes account for differences in beak sizes.

    2. character displacement

      When two competing species overlap in habitat, natural selection may drive one population to use resources that are not used by individuals of the other population. This allows two similar species to coexist.

    1. polarity of the NAO

      Polarity means to have two opposite or contradictory tendencies or aspects. In this case, the North Atlantic Oscillation (NAO) has both a warm phase and a cool phase, and convection (ocean mixing) differs between these conditions.

    2. 500-mb height of the atmosphere

      This 500-mb height (mb stands for millibar, which is a unit for measuring air pressure) is the typical height presented in weather maps. Since most weather occurs roughly around this height in the atmosphere, looking at 500-mb maps of the sky makes it possible to more accurately predict weather events.

    3. altimetric

      Altimetry is a technique for measuring the height of the surface below the altimeter. Satellites do this by sending a radar pulse to the surface of Earth. The time it takes for the pulse to bounce off the surface and return to the satellite is used to measure height, or altitude. Combined with precise satellite location data, such satellite measurements yield sea-surface heights.

    4. TOPEX/Poseidon

      Launched in 1992 as a joint mission of the U.S. and French space agencies, TOPEX/Poseidon was the first major oceanographic research satellite in space. It's goal was to map the topography of the ocean surface.

    5. sea-level pressure

      The sea-level pressure is the atmospheric pressure at a given location in the ocean. Because pressure and temperature are correlated, changes in temperature that result from climate change can, in turn, change sea-level pressure. 

    6. convection and/or subduction

      Convection is the movement of a fluid due to changes in density, where more dense waters sink and less dense waters rise. Subduction is the term for the downwards movement of a substance, in this case when one water mass moves below another.

    7. coupled air-sea general circulation model

      To accurately predict conditions on Earth, models of ocean currents and circulation are connected, or coupled, with models of atmospheric, ocean, and sea ice dynamics.

    8. basin-scale forcings

      The mechanisms causing ocean temperatures to increase are likely the same for every ocean.

      Examples include the radiative forcings from volcanic aerosols, stratospheric ozone depletion, greenhouse gases, and solar variability.

    9. statistically significant,

      The likelihood that a relationship between two or more variables is caused by something other than random chance. The data suggest there is a real difference in the temperature values between 1955-59 and 1970-74, as well as between 1970-74 and 1988-92.

    10. subarctic

      Ocean regions between latitudes 50°N and 70°N are subarctic.

      In subarctic oceans, there is a large range of temperature variation through the year, with cold winters and moderately warm summers. These latitudes also experience deep ocean mixing due to strong winter storms.

    1. enterotypes

      A classification of living organisms, similar to ecosystems, based on their bacteriological ecosystem. They are identifiable constellations of intestinal bacteria, biological communities of microorganisms in the gut. Dr. Peer Bork discovered three human gut types in April 2011: Bacteroides, Prevotella and Ruminococcus.

    2. ulcerative colitis

      Chronic intestinal disease characterized by flares of inflammation of the innermost lining of the large intestine and rectum. Symptoms such as diarrhea, abdominal cramps, and bloody stools may occur alternating with quiescent (inactive/dormant) periods. Patients with ulcerative colitis are at an increased risk of developing colon cancer.

    3. generalized linear model analysis

      A statistical model used to describe associations between multiple independent and dependent variables. The goal is the optimal linear combination of parameters to explain an observation.

    4. alpha-diversity

      Alpha-diversity is a measurement of the diversity within a single community/ecosystem. In this study, the researchers found that all of the 69 factors correlated with both the average species diversity and abundance in all samples.

      Check out this video to learn more about alpha-diversity in the context of the microbiome.

    1. polynucleotide

      Poly means many, and a nucleotide is the building block of genetic material. Therefore, a polynucleotide is a chain of many nucleotides—or one strand of genetic material.

    2. carboxyl end

      The carboxyl end refers to the carboxylic acid group exposed on the protein chain. (Remember the analogy of kids lined up holding hands? This is in the Glossary annotation of "amino end.")

    3. mutagens

      An agent that changes one base into another either by chemical methods or radiation. Acridine is not a mutagen since it does not modify existing bases in DNA, but rather adds or deletes bases.

    1. Type VI CRISPR-Cas systems

      CRISPR is a family of DNA sequences that are part of the immune system of bacteria. CRISPR enzymes detect specific viral DNA or RNA sequences, and can cleave the invading sequences and destroy them. Recently, researchers have begun to use CRISPR as a highly accurate tool for detecting specific DNA sequences in their research.

      Type VI CRISPR-Cas systems are those that involve the protein Cas13, which can cut RNA molecules.

    2. ortholog

      Genes in different species that can be traced to a common ancestral DNA sequence.

      There are many different Cas9 and Cas13 orthologs from different bacterial organisms. As engineers, the researchers test many of them as they will have different levels of activity in mammalian cells (as compared to bacterial) and some might not work at all.

    3. nonhomologous end joining (NHEJ)

      When both strands of DNA are cut, a cell can repair the DNA by rejoining the two strands. Nonhomologous end joining is one way this repair can happen, and it does not require homologous (similar) sequences.

      Because the sequences do not have to be homologous, this process is imprecise and can result in deletions or insertions.

    4. homology-directed repair (HDR)

      A process of precise DNA editing in which a cell uses homologous (similar) sequences as a template to repair DNA.

      This method is more precise than nonhomologous end joining (NHEJ), but takes more time. It's also generally less efficient and does not operate on non-dividing cell types like neurons.

    5. catalytically inactive

      The job of enzymes is to make chemical reactions happen faster. An enzyme that is catalytically inactive does not accelerate chemical reactions.

      Cas13 catalyzes the cleavage (cutting) of RNA molecules. This is an important function of the bacterial immune system, where Cas13 helps protect the organism from invading RNA.

      To use Cas13 for RNA editing, the researchers created a catalytically inactive enzyme (dCas13) that can be used to target RNA without cutting it and allowing for recruitment of other enzymes to the RNA.

    6. endogenous editing of transcripts

      RNA editing happens in the cell after DNA has been transcribed (RNA molecules have been synthesized from a using a DNA sequence as a template). This editing is usually insertion, deletion, or substitution of bases. The most common type of RNA editing is the substitution of adenosine to inosine, which functionally reads as guanosine (facilitated by the ADAR family of enzymes). Essentially, this reads as an A to G base change.

    7. Endogenous

      Native to a system (i.e. not the result of changes by external factors). Endogenous targeting here means the normal target sites for the ADAR protein in the cell.

    8. cloned

      Cloning means to insert a gene, a gene fragment, or an accessory sequence into a vector. Vectors are vehicles that carry DNA into a cell and exist as a plasmid in the nucleus,

      When the vector is multiplied in a cell or in a cell-free system, many copies of this fragment (clones) are generated.