September 24

September 24 - September 24, 2010 Much of what we know...

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September 24, 2010 Much of what we know about DNA replication has been gleaned form studies using prokaryotes (like E.coli) and viruses (like SV40 that infects monkeys) DNA replication in the nucleus A virus gets into the nucleus and then is replicated and is exported using eukaryotic secretion pathway 2 DNA polymerases involved in replication for an SV40 replication fork SV40 replication begins with the large T-antigen o Only viral encoded protein involved in SV40 replication o Hexamer o Helicase o Encoded by the viral genome Viruses tend to have small genomes that are easy to replicate, but have one or two proteins that allow them to take over the cell Use the machinery of the cell to replicate Build up large populations of the virus in the cell Sometimes the cells lyse and secrete large quantities of the cell, or sometimes the viruses are secreted Large T-antigen functions as a helicase o Dissociation of the hydrogen bonds Supercoiling is prevented by topoisomerases which clip the DNA strands which then unwind and then rejoin o Some just form nicks, which causes a swivel so the DNA helix can unwind itself Large T-antigen binds only to SV40 and only at the origin of replication Replication Protein A (RPA) (Eukaryotic Protein) o Binds to single stranded DNA o Keeps DNA in optimal conformation by DNA polymerase o Prevents the two separated strands from reassociating and reforming the original helix o Beta sheets act as shields and single stranded DNA fits into grooves Synthesis of the leading strand is catalysed exclusively by DNA
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This note was uploaded on 10/23/2010 for the course BIOL BIOL 200 taught by Professor Bureau during the Fall '09 term at McGill.

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September 24 - September 24, 2010 Much of what we know...

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