Exonuclease Activities of
DNA Polymerases
Initiation of Replication
*Strands must separate•DnaA•Helicases (DnaB and DnaC)•SSBPs (Single Stranded Binding
Proteins)•DNA gyrase (topoisomerase)
*Primase
Initiation of Replication
The sliding clamp
The two strands of a double helix are antiparallel•Continuous DNA synthesis = leading strand•Discontinuous DNA synthesis = lagging strand
DNA Synthesis
DNA Synthesis
DNA Synthesis
Completing the process
DNA Synthesis•Eukaryotes
•DNA unwinds at a replication origin •Two replication forks form •Bidirectional synthesis of DNA
•Much more DNA; complexed with proteins
•Eukaryotes have much more DNA
•Yeast 250-400 replicons •Mammalian cells up to 25,000
•Solution:
Multiple replication origins
•Yeast 4X that of E. coli •Drosophila 100X that of E. coli
