In the chimpanzee (Pan troglodytes), the haploid number of chromosomes is 24. How many sister chromatids are present in the G2 phase of a somatic cell, such as a cell in the bone marrow of the chimpanzee?

A. 12

B. 24

C. 48

D. 96

D

This question proved to be too hard for most candidates, with only 15 % answering correctly lower than the expected 25 % success rate from guessing. Most candidates thought that the diploid number of chromatids are present in a cell during G2. At that stage of the cell cycle, each chromosome has been replicated so there are twice the diploid number of chromatids. Candidates may not have known the difference between chromatids and chromosomes or that replication has already happened in G2, or perhaps they did not read the question carefully enough.