The diploid character of eukaryotic cells may mask the appearance of mutation since:

A. this may be a frame shift
B. the mutation is often reversible
C. the mutation may be palindromic
D. the matching chromosome may carry the dominant gene.
Please help. Thank you.

To determine the correct answer, let's break down the options and analyze them one by one:

A. Frame shift mutations: Frame shift mutations can result in a significant alteration in the protein sequence, potentially leading to malfunctions. However, diploid cells have two copies of each chromosome, so even if a frame shift mutation occurs in one copy, the other copy may act as a backup and still produce functional proteins. Therefore, A is not the correct answer to why the diploid character of eukaryotic cells may mask the appearance of mutation.

B. Reversible mutations: Reversible mutations refer to mutations that can be corrected or repaired by the cell's DNA repair mechanisms. While some mutations can indeed be repaired in diploid cells, this is not a universal characteristic, and not all mutations are reversible. Therefore, B is not the correct answer.

C. Palindromic mutations: Palindromic mutations involve DNA sequences that read the same forward and backward. However, the diploid nature of eukaryotic cells does not directly influence the occurrence of palindromic mutations. So, C is not the correct answer.

D. Dominant genes on the matching chromosome: In diploid cells, there are two copies of each chromosome, one inherited from each parent. If a mutation occurs on one copy of the chromosome and the matching chromosome carries the dominant gene, the dominant gene can mask the effects of the mutated gene. This means that even though a mutation may be present, it will not be observable because the dominant gene overrides its expression. Therefore, D is the correct answer.

In conclusion, the correct answer is D: the matching chromosome may carry the dominant gene.