Final answer:
In the context of fluorescence-activated cell sorting (FACS), without a specific figure, it's not possible to definitively determine the cell cycle phase of fraction 'C'. Generally, a single sharp peak would suggest cells in G1, but if DNA content has doubled, it would indicate G2 phase, and an intermediate increase suggests the S phase.
Step-by-step explanation:
Fluorescence-activated cell sorting (FACS) separates cells based on their fluorescent characteristics following the staining of specific cellular components such as DNA. When examining a FACS experiment where cells are sorted into different fractions labeled A to D, cells in fraction C would represent a point in the cell cycle where their DNA content is characteristic of that specific phase. In most cases, a single sharp peak in a FACS analysis, if corresponding to DNA staining, would likely represent cells in the G1 phase where the DNA content is not duplicated as it would be post-S phase.
However, without a specific figure provided, a definitive answer can't be given. If the 'C' fraction on a FACS graph shows a DNA content that is double the 'A' fraction on the same graph, it represents the G2 phase of cell division, where all cellular contents have been duplicated. By contrast, if the DNA content in the 'C' fraction is higher than 'A' but has not doubled, this would suggest the cells are in the S phase of the cell cycle where DNA is being replicated.