Question

What structural features of DNA makes semi-discontinuous replication necessary?

Answer 1

The DNA replication is a directional event. It only occurs in 5'-3' direction. During the time of replication the two strands of DNA got separated and each will act as a template for new strand to synthesise, like wise it duplicate. While replicating 3-5' strand the the newly synthesising strand has got right direction that is 5'-3' direction of polymerase enzyme. But while replicating 5-3' strand the newly synthesising strand that is in 3-5' direction which is opposite direction of polymerase movment, hence that has to be corrected. 3-5' DNA forms a small localised loop at the site of replication inorder to correct the direction of newly synthesising 3-5' DNA strand. Polymerase replicate stretch of DNA Iin that loop to obtain 5-3' direction. after a small stretch got replicated the loop is dissolved and forms another loop in forward direction. A cut would be left where loop is dissolved and it forms a discontinous stretches of DNA. But the replication of 3-5' DNA is continous as the newly synthesising DNA from it has the direction matches with polymerase.

Hence, if we consider the replication of DNA one strand is continous and other is discontinuous making the process semi-discontinuous.