Question

(b) Based on the data for the groups of cells cultured with 0.1% serum (groups 3 to 7), identify the groups(s) most likely to include cells undergoing mitosis.

AP Biology FRQ

Answer 1

In an AP Biology experiment with cells cultured in 0.1% serum, groups of cells observed soon after a radioactive pulse, typically groups 3 and 4, are most likely undergoing mitosis since the label hasn't had time to distribute in interphase cells.

Step-by-step explanation:

Based on the AP Biology scenario involving groups of cells cultured with 0.1% serum, it's key to analyze the chase periods to identify cell groups most likely undergoing mitosis. Looking for cells labeled after chase periods will guide our deduction. If we see that after a 4-hour chase a few cells that were in mitosis were labeled, the shorter the chase period, the higher the chance we have of finding cells in mitosis since the label hasn't had time to distribute widely in the interphase cells. This suggests that groups with the shortest chase period after synchronization should have the highest number of cells in mitosis. Typically, such a chase experiment would involve a pulse of radioactive thymidine for a period, followed by a chase with nonradioactive thymidine, with the labeled cells indicating the ones that were undergoing DNA synthesis at the time of the pulse. Therefore, the groups most likely to include cells undergoing mitosis would be those observed the soonest after the pulse, typically groups 3 and 4, based on a general understanding of cell cycle progression.

Answer 2

Groups 4 to 7 are most likely to be undergoing the mitotic phase of the cell cycle.

Step-by-step explanation:

Since the four proteins used p16, p18, p21, and p27 are inhibitors of cyclin-dependent kinases (CDK), their absence indicates that the cell is undergoing mitosis - the cell cycle is regulated by CDKs. In the absence of these inhibitors, the cell cycle moves on forward. Because the bar for DNA replication is longer in the case for groups 4 to 7, it is indicative of the fact that these cells have gone through the mitotic phase.

Hope that answers the question, have a great day!