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Chapter 3

BIL 250 Chapter Notes - Chapter 3: Okazaki Fragments, Telomerase, Dna Ligase

Course Code
BIL 250
Kevin Mc Cracken

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CHAPTER 3: DNA Replication
Models of DNA:
Semi conservative- ½ parent generation to both DNA
Conservative- 1 whole DNA passed and one new one
Dispersive- parental dispersed to new helixes
Meselson and Stahl made a centrifuge of 15N DNA composition and as it replicated, the
products were 14/15 DNA and 14 DNA. This showed that DNA is semiconservative rather than
conservative or dispersal.
MAIN MANZ: Arthur Kornberg
Discovered mechanisms of DNA synthesis
Four things necessary for DNA synthesis:
1. dNTPs: dATP, dTTP, dGTP, dCTP (sugar base and three phosphates) (precursor to
DNA/ before the two phosphates are released)
2. DNA Template
3. DNA Polymerase (my manz Kornberg’s enzyme)
4. Mg2+ which helps polymerase
Three Features of DNA synthesis:
1. Poly I helps to form the phosphodiester bond between the 3’ OH and the 5’ dNTP
2. Poly helps to identify which complementary dNTP to use during elongation
3. 5’ → 3’
Exonuclease Activity: where the nucleotides can be removed if necessary (proofreading)
3’ to 5’ usually
5’ to 3’ in DNA repair and replication
Polymerase alpha nuclear DNA replication No
Polymerase beta Nuclear DNA repair No
Polymerase gamma Mitochondrial DNA replication Yes
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