How were the internal signals that control the transitions between stages of the cell cycle discovered?
A) By looking at DNA sequences at different stages of the cell cycle
B) By looking at RNA sequences at different stages of the cell cycle
C) By fusing different cells together
D) By examining changes in the mitotic spindle
E) None of the above

Question

Quizplus · Accepted Answer

The discovery of internal signals that control the transitions between stages of the cell cycle was made by fusing different cells together. In particular, experiments with fusing a non-dividing cell with a dividing cell showed that the non-dividing cell could trigger the dividing cell to enter into the S phase, providing evidence for the existence of a signal that promotes the transition from G1 to S phase. Similar experiments with fusing cells at different stages of the cycle led to the identification of additional signals that control other transitions within the cell cycle.

How Were the Internal Signals That Control the Transitions Between