- Nov 2024
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www.youtube.com www.youtube.com
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we now realize the base pairs come to join each other up together as the system unravels and forms a new pair of DNA molecules well up to a point it does and that point is known to be accurate to about one in 10,000 base pairs now if you and I wrote an article and there was only one typo in a 10,000w article we'd be very pleased but this is nowhere near enough for a DNA sequence of three billion base pairs there would be half a million at least of Errors
for - DNA replication accuracy - 1 in 10,000 - too high for successful replication - another higher level mechanism to correct for these errors - need a whole body for that - Denis Noble
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- Nov 2022
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www.wikipathways.org www.wikipathways.org
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Can broadly split the process into three parts. Initiation, elongation and termination
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DNAPolymerase A
Primase and DNA polymerase A work in close association.
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CDK2
This is the S-phase CDK.
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Assembly of the pre-replicative complex
- Replication origin licensing.
- All of this occurs in G1 phase
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Orc complex
Orc1-5 complex.
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Cdc6
Cdc6 is only present in G1 phase.
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DNA replication pathway in humans. Orc complex binds the origin of replication.
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bio.libretexts.org bio.libretexts.org
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The initial sample consisted of 1 band. F = 0. 1st generation = The sample overall less dense, still one band. Intermediate density. dsDNA made of one strand heavy and one light. After 2 generations, there was a band for intermediate density and for strands of just light, N-14, dsDNA.
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Three methods of replication were initially hypothesized: * Conservative * Semi-conservative * Dispersive
Semi-conservative method was eventually determined to be correct based on empirical evidence from Messelson & Stahl, in 1958.
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Parental strands consist of N-15 isotopes. Replicated daughter strands consist of N-14 isotopes. The CsCl ultracentrifugation process creates density gradient. This allows DNA fragments of different densities to migrate and form a band at the point at which their buoyant density equals that of the salt.
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- E.coli grown in an heavy nitrogen, N-15, enriched medium
- Then transferred to N-14 based media to reproduce
- As several points in the experiment, cells were lysed and underwent ultracentrifugation through a CsCl concentration gradient
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