2. Which of the following is/are TRUE? (Select ALL that are
TRUE.)

a. The p53 protein is stable and active in the cell only when
the cell has damaged DNA.

b. Because the normal function of the active p53 protein is to
promote entry into S phase of mitosis, loss of p53 activity by
mutation of both copies of the p53 gene does not lead to
tumors.

c. The retinoblastoma protein Rb becomes active (binds to and
inhibits a transcriptional regulator) in response to mitogen
binding to a RTK.

d. A loss-of-function mutation in a mitogen-activated RTK (the
kinase activity of the RTK is knocked out) is likely to lead to a
tumor by causing inappropriate cell proliferation.

e. A gain-of-function mutation in a mitogen-activated RTK in
which the RTK formed dimers in the absence of ligand is likely to
lead a tumor by causing to inappropriate cell proliferation