2. Why is DNA replication slightly slower in the lagging strand of DNA than in the leading strand? Use specific examples.
DNA replication is slightly slower in the lagging strand of DNA compared to the leading strand due to the nature of how DNA polymerase functions and the direction in which it synthesizes new DNA strands.
1. Okazaki Fragments: In the lagging strand, DNA polymerase synthesizes short segments of DNA called Okazaki fragments. These fragments are synthesized in the opposite direction of DNA unwinding, which means that the polymerase has to continually stop and restart synthesis as the replication fork opens up. This process of discontinuous replication in the lagging strand results in a slower overall rate of replication compared to the continuous synthesis on the leading strand.
2. Priming: The lagging strand requires multiple RNA primers to initiate DNA synthesis on each Okazaki fragment. These primers must be removed and replaced with DNA nucleotides before the fragments can be joined together, adding additional steps and slowing down the overall replication process.
3. Proofreading: DNA polymerase has proofreading capabilities to correct errors in DNA synthesis. However, the lagging strand requires more frequent proofreading as multiple primers are being used, leading to a slightly slower rate of replication compared to the leading strand.
Overall, the combination of discontinuous synthesis, the need for multiple primers, and increased proofreading in the lagging strand results in a slightly slower rate of DNA replication compared to the leading strand.