Final answer:
The length of the G2 phase is the time between the end of the S phase and the beginning of mitosis. Based on the information that the radiolabeled mitotic figures are observed 6 hours after the introduction of the radiolabel and the typical 24-hour cell cycle, the length of the G2 phase can be estimated at around 4.5 hours.
Step-by-step explanation:
The question pertains to the length of the G2 phase of the cell cycle in asynchronously dividing cells. Based on the scenario provided, where the first radiolabeled mitotic figures appeared 6 hours after the radiolabel was introduced, the duration of the G2 phase can be calculated by subtracting the known time it takes for a cell in an asynchronous culture to progress from the beginning of mitosis to the time the radiolabel was introduced. Considering a typical 24-hour cell cycle for rapidly dividing human cells, the S phase lasts approximately 10 hours, followed by the G2 phase. Using this information, if mitosis (M phase) occurs 0.5 hours after the G2 phase, then the G2 phase is the duration between when the S phase ends and mitosis begins.
Given that the radiolabeled mitotic figures appear 6 hours after the introduction of the radiolabel and if the S phase just finished when the radiolabel was introduced, we must subtract the duration of mitosis (0.5 hours) from the 6 hours to obtain the length of the G2 phase. Therefore, the duration of the G2 phase would be 6 hours minus 0.5 hours, which equals 5.5 hours. However, since 5.5 hours is not an option here, we must reconsider the options given. In the options provided, the closest value to the calculated duration of the G2 phase is 4.5 hours (Choice A), which aligns with the typical length of the G2 phase provided in the instructions.
\