5. Analyzing a family's traits
Cindy is a beautiful teenager who becomes very upset when her hair begins to fall out in
big patches. Her sister Lynn is not experiencing hair loss, but their mother, Judy, states
that she has been losing her hair for years. The girls' maternal grandmother also lost hair,
although the maternal grandfather (mother's side), and the two paternal grandparents
(father's side) all have full heads of hair. This condition of hair loss is called alopecia
areata and is inherited as an autosomal dominant trait.
Construct a pedigree to represent the expression of alopecia areata throughout three
generations in Cindy's family. Under each symbol, write the person's name. Next to
each symbol, write the letters representing that person's known genotype (AA, Aa, aa,
or A
If Cindy marries a man with no evidence of alopecia in his family, what is the prob-
ability that their first child will have alopecia areata?
Cindy
Probability?