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
34.1: DNA Replication Polymerases
Arthur Kornberg (1918‐2007) Nobel Prize 1959.
“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”.
1.
2.
3.
4.
Deoxynucleoside-5’-triphosphates
Template DNA strand
Primer
Error Correction
DNA Pol I Klenow fragment:
5’→3’ polymerase activity
3’→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
Pol III: Polymerase
error = 10-5, nuclease
error 10-2; Overall
error rate = 10-7
3’→5’ Exonuclease Proofreading
DNA Replication Requires Unwinding
Helicase
Gyrase inhibitors
Topoisomerase
Type I topoisomerase: relax supercoiled DNA.
Type II topisomerase (gyrase): add negative supercoils to DNA (requires
ATP).
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