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.


Ans: d. phosphorylation of RB by Cdk4 and Cdk2.

Biology & Microbiology

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