[Campbell Biology P.293] The cell fusion experiments described in the 'The Cell Cycle Contro... | Practice Question

The cell fusion experiments described in the 'The Cell Cycle Control System' section strongly support which of the following hypotheses?

  • A: The cell cycle is primarily controlled by the size of the nucleus.
  • B: Specific signaling molecules in the cytoplasm drive progression through the cell cycle.
  • C: Each phase of the cell cycle is independently regulated by nuclear factors.
  • D: Chromatin condensation is the sole trigger for initiating mitosis.

Explanation

The cell fusion experiments showed that a cell in G1 phase would immediately enter S phase when fused with an S phase cell, and any cell would enter M phase when fused with an M phase cell. This strongly indicates that cytoplasmic signaling molecules are responsible for driving the cell cycle.