BIO325 - Lecture 4 - BIO325 24 January 2008 DNA Replication...

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BIO325 24 January 2008 DNA Replication (cont.), DNA Transcription A. Replication in Mammals a. Mammals have multiple origins of replication to account for large amount of DNA i. Bidirectional replication at each replication bubble, eventually meeting each other b. Mammals have linear chromosomes c. DNA polymerase alpha i. 5’ to 3’ RNA polymerase activity ii. 5’ to 3’ DNA polymerase activity iii. Does not proofread 1. No exonuclease activity iv. Low processivity v. Uses first active site to make an RNA primer from RNA nucleotides solution surrounding DNA and connects them with phosphodiester bonds 1. Smaller than RNA primer than in prokaryotes 2. Small enough that it would fall off if DNA pol alpha would release vi. Uses other active site to add DNA bases, then falls off d. DNA polymerase delta i. Major replication enzyme in mammals (humans) ii. 5’ to 3’ DNA polymerase activity iii. 3’ to 5’ exonuclease activity 1. Recall : Proofreading iv. High processivity 1. High accuracy, High speed v. Has a clamp that causes it to have high processivity vi. Fills in gap where primer used to be after exonuclease removes it vii. Can run all the way to the end to the very last nucleotide 1. Makes a perfect and complete copy in the leading strand e. No DNA polymerase with 5’ to 3’ exonuclease activity in eukaryotes that is equivalent to prokaryotic DNA pol I f. Exonuclease i. Has 5’ to 3’ exonuclease activity
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BIO325 - Lecture 4 - BIO325 24 January 2008 DNA Replication...

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