How does the likelihood of a mutational event occurring vary during different phases of the cell cycle?

During which part of the cell cycle is the likelihood highest that a mutational event occurs?

a. S-phase
b. Metaphase of M-phase
c. G-2 phase
d. Anaphase of M-phase
e. G1-phase

Answer:

The likelihood of a mutational event occurring is highest during the S-phase of the cell cycle.

During the S-phase, DNA replication takes place, and the DNA is being actively copied. This process involves the separation of the DNA double helix and the synthesis of new strands using existing ones as templates. This creates a window of vulnerability where DNA damage or errors in replication can occur, leading to mutations.

During the other phases of the cell cycle, the DNA is relatively stable and not actively being replicated, so the likelihood of mutations is lower. In the G1 phase, the cell is preparing for DNA replication, but the DNA is not yet being replicated.

In the G2 phase, DNA repair mechanisms are activated to ensure that any damage that occurred during replication is repaired before the cell enters mitosis. During metaphase and anaphase of the M-phase, the DNA is being separated and pulled apart, but it is not being replicated, so the likelihood of mutations is relatively low.