Genetically Knocking Out Both Copies of the P53 Gene in Rats

Question

Genetically knocking out both copies of the p53 gene in rats …
A) is embryonic lethal.
B) results in a lower malignancy rate, but the rats are otherwise seemingly normal.
C) results in a higher rate of cancer onset, but the rats are otherwise seemingly normal.
D) increases cell death by apoptosis, leading to developmental defects.
E) does not have any effect unless the rats live outside of the laboratory and are exposed to various types of stress.

Accepted Answer

Most rats (or mice) with a homozygous knockout of the gene encoding p53 develop cancer within a few months after birth but appear normal otherwise, suggesting that p53 function is required only in special circumstances.