Question

A research scientist is studying the effects of a novel enzyme inhibitor on DNA replication in eukaryotic cells. The inhibitor specifically blocks the activity of DNA polymerase a which leads to DNA joining. Which of the following consequences is most likely to be observed in the treated cells?

• A. The entire replication process will stop immediately, preventing both leading and lagging strand synthesis.
• B. The leading strand will be synthesized normally, but the lagging strand synthesis will be inhibited.
• C. Replication will be delayed due to an inability to synthesize RNA primers for both strands, but DNA replication will eventually proceed at a slower rate.
• D. The helicase enzyme will become inactive, preventing the formation of replication forks.

Answer 1

Answer: (A)

The entire replication process will stop immediately, preventing both leading and lagging strand synthesis.

Answer 2

DNA polymerase $\alpha$ is responsible for synthesizing RNA primers and a short DNA stretch at the beginning of new DNA synthesis on both the leading and lagging strands. Inhibiting this enzyme prevents primer formation. Since DNA polymerases require a primer to start synthesizing DNA, the absence of primers halts the initiation of DNA replication on both strands, effectively stopping the entire process.