Lecture 5-DNA Replication and Mitosis

Lecture 5-DNA Replication and Mitosis - Lecture 5- DNA...

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Lecture 5- DNA Replication and Mitosis S Phase -DNA replication occurs in S phase DNA Structure -Double helix of two antiparallel, covalently bonded sugar phosphate backbones -Backbones are held to each other by hydrogen bonding between complimentary base pairs; A with T, G with C -Distinct 3’ and 5’ end confers “polarity” on DNA strands -Strands run antiparallel -OH hydroxyl on the 3’ end; phosphate on 5’ carbon. These give the molecule its polarity Elongation by DNA Polymerase -All DNA polymerases can do only one thing: add a base to a 3’ OH end when a base is already there before. -If no base is already there, primase creates a short sequence of nucleotides (RNA sequence) to get the replication going. (Primase is a kind of RNA polymerase) -DNA polymerase builds one strand continuously, the other discontinuously Replication Forks -Replication is mediated by a complex of proteins -Semiconservative replication: one template strand, one new one (on both strands of the replication fork)
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Lecture 5-DNA Replication and Mitosis - Lecture 5- DNA...

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