In this exercise, you are asked to play the role of the genetic counselor advising a young healthy couples who are at the beginning stages or their pregnancies. Based on their own phenotypes, as well as those of their parents and grandparents, they seek help in predicting those of their offspring (HINT: you’ll probably want to draw diagrams of each situation, using uppercase to indicate dominant genes and lowercase to indicate recessive genes).
1. A man with red hair (recessive) marries a woman with black hair, whose mother had red hair. What are the chances that their first child will have red hair? ___________ Black hair?___________




2. A woman and a man both have brown eyes, but their first child has blue eyes, which is a recessive trait. What are the chances that their second child will have blue eyes?_________________




3. An apparently healthy couple has one normal daughter and then a son who develops a learning disability, an X-linked recessive disease. What are the chances that the boy’s sister is a carrier of the learning disability?_______________ What chance is there that she will develop the learning disability herself?________________





4. In dogs, there is a hereditary deafness caused by a recessive gene, “d.” A kennel owner has a male dog that she wants to use for breeding purposes if possible. The dog can hear, so the owner knows his genotype is either DD or Dd. If the dog’s genotype is Dd, the owner does not wish to use him for breeding so that the deafness gene will not be passed on. This can be tested by breeding the dog to a deaf female (dd). Draw the Punnett squares to illustrate these two possible crosses.














a. In each case, what percentage/how many of the offspring would be expected to be hearing?
i. ___________ % if male is DD
ii. ___________ % if male is Dd
b. Deaf?
i. ___________ % if male is DD
ii. ___________ % if male is Dd

c. How could you tell the genotype of this male dog?