In humans, having dimples in the cheeks is a dominant trait. If a child has dimples but only one of her parents does, what are the genotypes of her parents?

Question:-In humans, having dimples in the cheeks is a dominant trait. If a child has dimples but only one of her parents does, what are the genotypes of her parents?

A. One parent dd, other parent DD

B. one parent dd, other parent Dd

C. one parent Dd, other parent DD

D. one parent must be DD, the other parent could be either dd or Dd

E. one parent must be dd, the other parent could be either Dd or DD

Answer: E. one parent must be dd, the other parent could be either Dd or DD

The dominant trait dimples has the genotype of DD or Dd, and is so punished. Since the child is dimpled, she should have at least one D allele. If one parent lacks dimples, their genotype should be dd. The other parent has dimples and her genotype could be DD or dd.

To summarize:

• D is dominant over d

• The child has dimples, so must be a Dd or DD genotype.

• However, one parent lacks dimples hence is dd

• The other parent has dimples as well, so it could be DD or Dd.

Thus, the genotype of dimples parent could either be DD or dd while the non-dimples parent remains dd. The important aspect here is that as dimples are dominant, one without them must have two recessive alleles (dd), while a parent with dimples can be either DD or Dd. With one parent being dD and the other being either Dd or dD, we can infer genotype combination that leads to a child having dimples.