Consider a spontaneous mutation in the gene p53, a tumor supressor gene associated with breast cancer. Mutations happen at a rate of about 1 error per 10 9 bases per generation. A spontaneous deleterious mutation must occur in p53 specifically, and not in another gene. The likelihood that a spontaneous mutation is deleterious and could lead to cancer depends on the number of mutable bases in p53, the fraction of bases that will affect the function of p53, and that both p53 alleles are mutated.

A single cell will likely require mutations in both alleles of cancer‑associated genes such as p53 as well as a few other genes to cause the spontaneous cellular growth that leads to a tumor. Therefore, the likelihood of developing cancer from a spontaneous mutation also depends on the total number of cells in the body and the number of times each cell has replicated. Each cellular replication is another chance for a single spontaneous mutation to occur. Considering these factors, the likelihood of developing cancer from a spontaneous mutation should be extremely small.
Select the statements that best explain why cancer in general is still prevalent among humans, despite the extremely small probability of developing cancer from a spontaneous mutation.


A. Cancer is a complex disease that affects many tissues, and many of the mechanisms that cause those cancers are still unknown
B. Environmental factors, such as exposure to high levels of radiation. which causes deleterious mutations and rampant cell growth contribute to an increased nsk of mutation above the background error rate
C. No cure has boon found for any type of cancer, including those caused by HER2. and current treatments, such as radiation or chemotherapy, are largely ineffective.
D. An increased nsk of developing cancer can run In families For example, breast cancer and ovarian cancer are induced in hereditary breast and overman cancer syndrome, which can run in families