Final answer:
Processivity in DNA replication is aided by a sliding clamp that keeps DNA polymerase attached to the DNA template, enabling continuous synthesis of the leading strand and eventual joining of Okazaki fragments on the lagging strand.
Step-by-step explanation:
Processivity in DNA replication is facilitated by the sliding clamp, which holds the DNA polymerase in place on the DNA template, allowing the enzyme to efficiently synthesize a long strand of DNA without disassociating.
DNA replication is semi-discontinuous; the leading strand is synthesized continuously towards the replication fork, while the lagging strand is synthesized in short segments, known as Okazaki fragments, which are eventually joined together. The sliding clamp, a ring-shaped protein, plays a crucial role in processivity by encircling the DNA and serving as a mobile anchor for the polymerase enzyme during strand extension.
The anti-parallel nature of DNA creates a challenge during replication, as DNA polymerase can only synthesize DNA in the 5' to 3' direction. The enzyme topoisomerase prevents the over-winding of the DNA double helix ahead of the replication fork. This coordination of activities ensures that the replication fork can move rapidly, synthesizing DNA at a rate of about 1000 nucleotides per second.