In humans, dimples are a trait that exhibits simple dominance. The two alleles for this trait are dimples (D) and no dimples (d). A dimpled man whose mother has no dimples marries a woman with no dimples. What is the probability that their first child will have dimples?

The probability is ½

Explanation:

Since the dimple trait is simple dominance, it therefore can be inherited in both the homozygous (DD) and heterozygous form (Dd). For non dimples we have (dd).

Thus, for a dimpled man whose mother has no dimples, it can be concluded that he is an heterozygote. (For him to be dimpled with a non dimpled mom, his dad has to be either an homozygous/heterozygous dimpled man. Since his mom is non dimpled (dd), therefore he can only be an heterozygous)

Therefore, a cross between a dimpled man (Dd) and a non dimpled woman will give.

Dd x dd

Dd dd

½ ½

50% 50%

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