Tumor-suppressor genes normally control ...

A.

Sister chromatid separation

B.

Telomerase activity

C.

Protein degradation

D.

Cell proliferation or activation of apoptosis

E.

DNA polymerase processivity

The correct answer is letter D, tumor-suppressor genes normally control cell proliferation or activation of apoptosis.

Tumor-suppresor genes are actually normal genes that act and slow down cell division. They are also responsible for repairing DNA mistakes and they tell cells when to die (apoptosis).