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Exonuclease Activities of DNA Polymerases. Initiation of Replication. *Strands must separate •DnaA •Helicases (DnaB and DnaC) •SSBPs ( S ingle S tranded B inding P roteins) •DNA gyrase (topoisomerase). Initiation of Replication. *Primase. The sliding clamp.
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Initiation of Replication *Strands must separate •DnaA •Helicases (DnaB and DnaC) •SSBPs (Single Stranded Binding Proteins) •DNA gyrase (topoisomerase)
Initiation of Replication *Primase
The two strands of a double helix are antiparallel •Continuous DNA synthesis = leading strand •Discontinuous DNA synthesis = lagging strand
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 4X that of E. coli •Drosophila 100X that of E. coli •Solution: Multiple replication origins •Yeast 250-400 replicons •Mammalian cells up to 25,000