Question

A cell starts out in G2 phase with 12 chromosomes, but after mitosis, each of the daughter cells has only 11 chromosomes in G1 phase. What event provides the most likely explanation for this scenario?

A. During anaphase in the original cell, one of the centromeres didn't divide.

B. During prometaphase in the original cell, one of the chromosomes failed to attach to a spindle fiber.

C. The DNA in the original cell was not properly replicated in S phase.

D. This is not unexpected as the chromosome number drops between G2 and G1 phases of the cell cycle.

E. The original cell skipped metaphase during mitosis.

Answer 1

The most plausible explanation for a cell losing one chromosome after mitosis is that during anaphase, one centromere did not split properly, leading to one daughter cell missing a chromosome.

Step-by-step explanation:

If a cell starts out in G2 phase with 12 chromosomes, but after mitosis, each of the daughter cells has only 11 chromosomes in G1 phase, the most likely explanation for this discrepancy is option A: During anaphase in the original cell, one of the centromeres didn't divide. This failure in the division of the centromere means that one chromosome would not be pulled apart into two sister chromatids to be distributed equally among the two daughter cells. As a result, each daughter cell would end up with one less chromosome.

Option B is less likely since failure to attach to a spindle fiber would typically lead to a delay in mitosis until the problem is corrected. Option C refers to replication issues, which would have affected the chromosomal number already in the G2 phase. Option D is incorrect as the chromosome number is expected to remain the same after mitosis. Finally, option E is not feasible because skipping metaphase would disrupt the appropriate alignment and separation of chromosomes, affecting all rather than just one chromosome.