[Campbell Biology P.294] According to the experiments shown in Figure 12.14, what is the pri... | Practice Question

According to the experiments shown in Figure 12.14, what is the primary conclusion regarding the regulation of cell cycle progression?

  • A: Cell cycle progression is primarily controlled by the cell's internal clock, independent of external factors.
  • B: Molecules present in the cytoplasm during S or M phases can induce G1 nuclei to progress into those respective phases.
  • C: DNA duplication must be complete before a cell can enter mitosis.
  • D: G1 phase cells cannot proceed to S phase without external signals.

Explanation

The conclusion explicitly states: 'The results of fusing a G1 cell with a cell in the S or M phase of the cell cycle suggest that molecules present in the cytoplasm during the S or M phase control the progression to those phases.' This directly supports option B.