A researcher is studying a population of cells exposed to DN…

A researcher is studying a population of cells exposed to DNA-damaging radiation. Despite the damage, these cells continue through the cell cycle without pausing in G1. Further analysis reveals that p21 is not expressed in these cells. Which of the following is the most likely explanation for the absence of p21 activation?

You are analyzing a yeast mutant that accumulates high level…

You are analyzing a yeast mutant that accumulates high levels of active M-Cdk at 37°C but fails to exit M phase, even though M-Cdk and M-cyclin genes are unmutated. Which of the following temperature-sensitive mutations is most likely responsible for this failure to complete mitosis?