分子生物学 DNA复制机制 3 Unwinding of dnaB (helicase) the replication fork dnaG (primase) -Poly III Poly Ill- 子生物学教研室 RNA Poly I (erases primers primer,fills gap】 DNA ligase ●Ka2akd (connects fragments RNA loose ends】 strand Leading strand Okazaki fragment in A lagging strand Fig.6.15 Replication fork of Escherichio coli.A,Because new DNA can be synthesized only in the 5'-3'direction,one of the two new strands(the "lagging strand")is synthesized piecemeal.The primer has to be removed from the lagging strand by DNA polymerase I (Poly /)and the Okazaki fragments have to be connected by DNA ligase.B,Model for the actual assembly of proteins in the bacterial replication fork.Note that the DNA template for the lagging strand has to spool through the B clamp backward to account for the direction of DNA synthesis.B Clamp protein:clamp loader,dnaB,helicase:dnaC,primase:Poly DNA polymerasell.DNA的复制机制 DNA复制机制 分子生物学 生物化学与分子生物学教研室