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Lecture 06 2B03 2017.pptx - Lecture 6 DNA replication...

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Based on Chapter 28: DNA Metabolism: Replication, Recombination, and Repair Lecture 6 DNA replication, recombination and repair Part II 1
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Replication Factories DNA polymerases are immobilized in replication factories The factory is “fixed” to a cellular substructure It produces newly synthesized DNA as parental DNA duplex is fed in from the sides ( Unreplicated DNA goes in, Replicated DNA comes out ) Parental strands Daughter strand Origins of replication 2
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Why So Many DNA Polymerases? Different polymerases for different purposes They group into seven functional families Family A: polymerases for DNA repair in bacteria Family B: eukaryotic polymerases for replication of chromosomal DNA Family C: bacterial chromosomal DNA-replicating enzymes Families X and Y: act in DNA repair pathways Reverse transcriptases are retrovirus polymerases Telomerase renews ends of chromosome 3
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DNAPs Have a Common Architecture Their structures resemble a right hand Active site for polymerization is in crevice of palm Fingers grab dNTP Thumb is for DNA binding Blue dots: calcium ions Template DNA: gray Primer: Gold 4
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DNA Replication in Eukaryotic Cells Similar to prokaryotes, but more complex DNA in separate chromosomes (6 billion base pairs in 46 chromosomes in humans) – multiple replication sites – 20,000 in humans per cell Cell cycle controls the timing of DNA replication Eukaryotic cells contain more DNA polymerases (Table to follow) – 20+ DNA polymerase δ (delta) is the chief DNA replicase 5
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Eukaryotic Cell Cycle M: The stages of mitosis and cell division G1: characterized by rapid growth and metabolic activity S: the time of DNA synthesis G2: a relatively short period of growth when the cell prepares for division.
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