In each generation of this family after generation i, the age at diagnosis is significantly lower than would be found in nonfamilial (sporadic) cases of this cancer (~63 years). what is the most likely reason?

Option B, Hereditary (or familial) cases of this cancer typically occur at earlier ages than do no familial forms.

Explanation:

Image for this question is attached. Options for this questions are -

A.Members of this family know to be checked for colon cancer early in life

B.Hereditary (or familial) cases of this cancer typically occur at earlier ages than do no familial forms.

C.This is pure chance; it would not be expected if you were to look at a different family

D.This cancer requires mutations in more than this one gene

Solution-

The cause of early diagnosis of this genetic cancer form is done in order to detect the risk and guidance to reduce the risk at an early stage. Being familial in nature, this cancer form occurs at an early stage in the family members as compared to its non familial form. Genetic diagnosis will help in determining the pattern of transmission asap and hence will help in determining the risk that an individual may face so that precautionary measure can be taken  to suppress the problems caused due to this cancer.