Question

A mutant yeast strain stops proliferating when shifted from 25°C to 37°C. When these cells are analyzed at the two different temperatures, using a machine that sorts cells according to the amount of DNA they contain, the following graphs are obtained.

Which of the following would not explain the results with the mutant?
inability to initiate DNA replication
inability to begin M phase
inability to activate proteins needed to enter S phase
inappropriate production of a signal that causes the cells to remain in G1

Answer 1

The inability to activate proteins needed to enter S phase would explain the results with the mutant yeast strain that stops proliferating when shifted from 25°C to 37°C.

Step-by-step explanation:

The mutant yeast strain that stops proliferating when shifted from 25°C to 37°C can be explained by the inability to activate proteins needed to enter S phase. In normal cell cycle progression, the G1 phase is followed by the S phase, during which DNA replication occurs. If the mutant yeast strain is unable to activate the proteins necessary for entering the S phase, DNA replication cannot take place, leading to the halt in cell proliferation. This would explain the observed results obtained from analyzing the cells at both temperatures.