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? (d = dimples; d = no dimples)

The genotypes of her parents is that one parent must be dd, the other parent could be either Dd or DD.

Genotype is the part of the genetic make up of a cell, of an organism that determine the physical characteristic of the organism or an individual (phenotype). If the parent is dd which is recessive homozygous, he or she will contribute one d allele to the offspring, and then the child gets the other allele D, for dimple trait from the other parent whose is either DD or Dd.