Outline5 marksStandard
A student's diagram of DNA replication at a single replication fork shows the two parental strands (A and B) separating. On strand A, a single new strand (X) is being synthesized continuously towards the fork. On strand B, multiple short new strands (Y1, Y2, Y3) are being synthesized away from the fork, with gaps between them. Two enzymes are labelled: enzyme P is present at the growing ends of all new strands, and enzyme Q is located at the gaps on the Y strands.
Outline the process of semi-conservative DNA replication, explaining the roles of enzymes P and Q and why strand Y is synthesized in fragments rather than continuously.