DNA replication occurs at the same time in both strands of DNA. Why aren't both strands extended continuously (i. e. why is there a leading and lagging strand) ?

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Biology

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20 October, 22:13

DNA replication occurs at the same time in both strands of DNA. Why aren't both strands extended continuously (i. e. why is there a leading and lagging strand) ?

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Jakob Stevens · Answer 1

Because on the lagging strand DNA replication occurs in opposite direction to the unwinding of the double helix. That is it unwinds 5'-3' direction but DNA polymerase reads the template 3'-5' to synthesize 5'-3'. As a result it has to wait a little for enough nucleotides to be available to recreate a primer and elongate. This creates Okazaki Fragments.