This requirement has two fundamental consequences: (1) The lagging strand must have evolved The strand is synthesized in short segments, named Okazaki fragments, after their discoverer ( Sakabe and Okazaki 1966 Okazaki et al. This can onlyīe accomplished if the strand is made discontinuously ( Kornberg and Baker 1992). The other, or lagging strand, must be periodically extended away from the opening helix. One copied strand, called leading, canĬonveniently be extended in a continuous manner in the same direction that the helix must open to allow exposure of templatesįor polymerization. Polymerases confine the mechanisms that can be used by the cell for DNA duplication. The antiparallel structure of double-helical DNA and the 3′ end extension specificity of all DNA Replication of cellular chromosomal DNA is initiated by the multienzyme replisome machinery, which unwinds the DNA helix toĬreate a replication fork. That can shift from high efficiency to high fidelity. The eukaryotic maturation mechanism involves many enzymes, possibly three pathways, and regulation The eukaryotic fragments are much shorter, with lengths determined by nucleosome periodicity. Although the prokaryotic fragments are ∼1200 nucleotides long, Of the primer into a flap, flap removal, and then ligation. The lagging-strand fragments are initiated by RNA primers, which are removed by a joining mechanism involving strand displacement Identified proteins and multiple pathways responsible for maturation of the lagging strand. Genetic analyses and reconstitution experiments
The lagging strand needs to be processed to form a functional DNA segment. The leading strand is elongatedĬontinuously in the direction of fork opening, whereas the lagging strand is made discontinuously in the opposite direction. Cellular DNA replication requires efficient copying of the double-stranded chromosomal DNA.
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