Which of the Following Is True Regarding the RB Gene

Multiple Choice

Which of the following is true regarding the RB gene in relation to cancer and the cell cycle?
1) In many types of cancer both copies of the RB gene have been inactivated.
2) Inactivation of both copies of the RB gene impair the ability of the RB protein to bind E2F transcription factors.
3) pRB is phosphorylated through the action of cyclin-dependent kinases.

A) 1
B) 2
C) 3
D) 1 and 2
E) All of these