Lec7 - Lecture 7 DNA Replication 2(Lodish 6th Ed Chapter...

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Lecture 7 DNA Replication 2 (Lodish 5th Ed. Chapters 4.6 & 21.1-21.7)
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SSB SSB Summary of the steps in DNA replication
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Replication of Telomeres (ends of eucaryotic chromosomes) Lagging strand Leading strand
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The problem replicating linear chromosomes
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Telomerase extends the ends of chromosomes with a repetitive DNA sequence •Telomerase is a ribonuclear protein (150 nucleotide RNA and multiple protein subunits) • And a reverse transcriptase activity • RNA used as template for DNA synthesis
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Telomerase solves the problem of replicating linear chromosomes Telomerase is highly active in fertilized eggs, stem cells, and a few other cell types (including cancer cells) 3’ 3’ 3’ 3’ 3’ 3’
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5’ 5’ 3’ Lodish 6th ed Fig. 6-49
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Lodish 6th ed Fig. 6-49
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Telomerase extended template strand used for DNA synthesis Repetitive DNA
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Structure of Telomere during Interphase
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SV40 is a Model for Studying Eucaryotic DNA Replication • Small circular DNA tumor virus • One origin of DNA replication • An SV40 early gene makes T-antigen (tumor antigen) • T-antigen is an origin of DNA replication binding helicase (like DnaB protein) • When bound to SV40 or cellular origins, causes assembly of replication machinery
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Eukaryotic DNA Polymerases • DNA Polymerase α : eukaryotic “Primase” initiates DNA synthesis - Pol α is unique in its ability to initiate DNA synthesis by first synthesizing its own 12-nucleotide RNA primer and then extending it with about 20 bases of DNA (RNA-DNA primer). • DNA Polymerase
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Lec7 - Lecture 7 DNA Replication 2(Lodish 6th Ed Chapter...

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