A single autosomal gene controls eyelash length in humans. The allele for long eyelashes (LlD DDDdDd dd
) is dominant to a rare allele for short eyelashes (). The presence of dimples is controlled by a different autosomal gene that assorts independently from gene L. Individuals homozygous for the allele () always have extremely pronounced dimples. Heterozygous individuals () have moderate dimples, but the trait is incompletely penetrant, so 20% of individuals do not have visible dimples. Individuals of genotype do not have dimples.
Blanche is the only person in her family with short eyelashes. Blanche and her parents both lack dimples, but her maternal grandfather has extremely pronounced dimples (assume that Blanche’s father is genotype dd).
George has no history of dimples in his family. He has long eyelashes, as do his parents, but his maternal uncle (his mother’s brother) has short eyelashes.
Blanche and George are expecting a child. What is the probability that their child will have long eyelashes and dimples? Show your work. You should draw a pedigree and indicate genotypes where possible.
