Question

In the pedigree shown, the presence of a dominant autosomal genetic disorder is indicated by a shaded box. This is an autosomal inheritance, not a sex-linked trait.

Part A: Determine whether or not either of the parents (1 or 2) could be homozygous for the trait in question. Explain your answer in 1-2 complete sentences. (2 points)

Part B: “Person 8” does not want to see the disorder passed on to his offspring. He does, for certain, what to get married and have children biologically. If you were a genetic counselor, what advice would you give to him about his odds on having a child with the genetic disorder if he:

(a) Married a woman who is heterozygous for the condition and

(b) married a woman who does not have the genetic disorder. (2 points)

Answer 1

Part A:

No, neither of the parents could be homozygous for the trait.

If any of the parents were homozygous for the disorder, then all the offspring would inherit the disease, but offspring 5 did not get the disease. Hence, none of the parents was homozygous.

Part B:

It would be most appropriate to marry a woman who does not have a disease.

It is because it reduces the probability of offspring to have a disease.

When both the parent are heterozygous only 1/4 chances are there that the offspring would not have a disease.

In contrast, if the mother is homozygous recessive and father is recessive then 2/4 chances are there that the offspring would not have a disease.