Regulation of the Cell Cycle Is Dependent on Cyclins and Cyclin-Dependent

Multiple Choice

Regulation of the cell cycle is dependent on cyclins and cyclin-dependent kinases. The key(s) that allows a cell to progress beyond the restriction point is (are)

A) Cdk1 and cyclin B.
B) cyclin D and p21.
C) cyclin A and Cdk2.
D) phosphorylation of RB by Cdk4 and Cdk2.
E) external signals from growth factors.