Replication forks

Replication fork (Sechon 28 9) Point at which strands of double helical DNA separate... 

Lagging strand (Section 28.10) In DNA replication, the strand that grows away from the replication fork. 

Replication fork (Section 28.3) The point of unraveling in a DNA chain where replication occurs. 

Registiy of Mass Spectral Data, 412 Replication (DNA). 1106-1107 direction of, 1107 error rate during. 1107 lagging strand in, 1107 leading strand in, 1107 Okazaki fragments in, 1107 replication fork in, 1107 Replication fork (DNA), 1107 Reserpine, structure of, 65 Residue (protein), 1027 Resist, photolithography and, 505-506... 

Camptothecins. Figure 3 Conversion of reversible Topi -DNA cleavage complexes into DNA damage by collision of a replication fork (the DNA polymerase complex is not shown). 

Figure 36-17. The generation of "replication bubbles" during the process of DNA synthesis. The bidirectional replication and the proposed positions of unwinding proteins at the replication forks are depicted.

The pall of fog that has shrouded the sister separation process for over a century is starting to lift and this long mysterious process has started to reveal its secrets. There is now convincing evidence that the sudden movement of chromosomes to the poles at the onset of anaphase is triggered by cleavage of specific sister chromatid cohesion proteins. Future research must address the structural basis of cohesion and how it is established only at replication forks. It must also address the generality of mechanisms that dismantle cohesion at the metaphase to anaphase transition and how mistakes in this process contribute to human disease. 

DNA synthesis occurs in both directions at each of the rep-licating forks. Once a DNA strand has been primed, synthesis toward the replicating fork can be visualized as continuous. Growth of the opposite,... 

DNA replication proceeds in both directions from the replication origin (bidirectional), which means you need to form two sets of replication complexes. Each replication complex moves away from the origin (in opposite directions), unwinding and replicating both strands at each replication fork. 

At each replication fork there are two DNA polymerase complexes. As the double-stranded DNA is unwound, two template strands are exposed. One of the templates can be replicated in a continuous fashion by DNA polymerase since a continuous synthesis of new strands can occur in the 5 to 3 direction as the template strand is exposed. Since all growing chains must be synthesized in file 5 to 3 direction, the lagging chain must be continuously reinitiated as new template is exposed. The lagging strand is then synthesized discontinuously, in pieces that must be joined together later. 

Figure 4.26 (a) DNA replication at low resolution (for example as seen by electron microscopy). Only one replication fork is visible and it appears that both strands of the parental DNA replicate continuously in the same direction, which cannot be the case, since the two strands of parental DNA are anti-parallel, (b) The problem is solved by the priming of DNA synthesis with short RNA primers, whose 3 -hydroxyl can be used by DNA polymerase, producing Okazaki fragments, while on the other strand, DNA synthesis is continuous. (From Voet and Voet, 2004. Reproduced with permission from John Wiley Sons., Inc.)... 

Laskey, R. A. and Madine, M. A. A rotary pumping model for helicase function of MCM proteins at a distance from replication forks. EMBO Rep 2003, 4, 26-30. 

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