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CHAPTER 34: DNA Replication Problems 1-6, 9-10,12,17 Genetic information Archive Blueprint Copying Transcription Translation Bioinformatics Metabolic networks Regulatory networks Systems Biology

CHAPTER 34: DNA Replication - ccrc.uga.edurcarlson/bcmb3100/Chap34.pdf · CHAPTER 34: DNA Replication Problems 1-6, 9-10,12,17 Genetic information Archive Blueprint Copying Transcription

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CHAPTER 34: DNA ReplicationProblems 1-6, 9-10,12,17

Genetic information Archive Blueprint Copying

Transcription TranslationBioinformatics

Metabolic networks Regulatory networks Systems Biology

34.1: DNA Replication Polymerases

“Throughout college I worked evenings, weekends, and school holidays as a salesman in men’s furnishings stores. This left little time for study or sleep and none for leisure. With these earnings, a New York State Regents Scholarship of $100 a year, no college tuition, and frugal living, I saved enough to see myself through the first half of medical school at the University of Rochester.”Arthur Kornberg, from his book “Never a Dull Enzyme”.

Arthur Kornberg (1918‐2007) Nobel Prize 1959.

1. Deoxynucleoside-5’-triphosphates2. Template DNA strand3. Primer4. Error Correction

DNA Pol I Klenow fragment:5’→3’ polymerase activity3’→5’ exonuclease activity

The 5’→3’- exonuclease activity is present in another portion of the Pol I protein not shown here.

DNA Polymerization occurs with high fidelity due to specificity and error correction

Induced Fit

3’→5’ Exonuclease Proofreading

Pol III: Polymerase error = 10-5, nuclease error 10-2; Overall error rate = 10-7

DNA Replication Requires Unwinding

Helicase

Topoisomerase

Type I topoisomerase: relax supercoiled DNA.Type II topisomerase (gyrase): add negative supercoils to DNA (requires ATP).

Gyrase inhibitors

34.2: DNA Replication is Highly Coordinated

An Origin for DNA Replication

A helicase

• Replication involves initiation, elongation, and termination.

• E. coli chromosome is circular, double-stranded DNA (4.6x103 kilobase pairs, >1000 bp/sec)

• Replication begins at a unique site (origin)• Proceeds bidirectionally until the two replication

complexes meet (termination site)• Replisome - protein machinery for replication

(one replisome at each of 2 replication forks)

DNA Replication Requires a Primer, is Both Continuous and Discontinuous, Processive, and Coordinated.

Continuous and Discontinous

Okazaki Fragments

Joining of Okazaki fragments by DNA pol I and DNA ligase

DNA Replication in Eucaryotes: Telomeres Multiple origins and replicons Licensing factors Polymerase Polymerase Polymerase switching