How many mutated alleles of a proto-oncogene are necessary to potentially cause cancer?

The correct answer is that one mutated allele of a proto-oncogene is sufficient to potentially cause cancer. Proto-oncogenes are normal genes that promote cell growth and division. When these genes are mutated, they can become oncogenes, which can drive excessive cell proliferation and contribute to tumor formation.

In general, only a single mutation in one of the alleles of a proto-oncogene is necessary for the gain of function that characterizes oncogenes. This is because most proto-oncogenes act in a dominant manner, meaning that the presence of just one mutant allele is enough to trigger the oncogenic behavior. This contrasts with tumor suppressor genes, where mutations in both alleles are typically required to eliminate their growth-inhibitory effects.

In summary, a single mutated allele of a proto-oncogene can initiate a cascade of events that may ultimately lead to cancer, making the understanding of these mutations crucial in cancer biology and treatment strategies.