K.S. comes for a clinic visit to determine whether she is pregnant. She is very concerned because she suspects there may be a genetic disease in her family. On further questioning, you find out that her brother’s son has the disorder. Her brother’s other children (a boy and a girl) are unaffected. K.S.’s parents, grandparents, and other siblings (a brother and two sisters) do not have manifestations of the disorder. Her brother’s wife has said that she thinks one of her distant relatives may have had the disease.   Discussion Questions   If the disorder is indeed inherited as a single-gene defect, do you think it is autosomal dominant, autosomal recessive, or X linked? Justify your answer.

K.S. comes for a clinic visit to determine whether she is pregnant. She is very concerned because she suspects there may be a genetic disease in her family. On further questioning, you find out that her brother’s son has the disorder. Her brother’s other children (a boy and a girl) are unaffected. K.S.’s parents, grandparents, and other siblings (a brother and two sisters) do not have manifestations of the disorder. Her brother’s wife has said that she thinks one of her distant relatives may have had the disease.

Discussion Questions

1. If the disorder is indeed inherited as a single-gene defect, do you think it is autosomal dominant, autosomal recessive, or X linked? Justify your answer.
2. Construct a pedigree chart and predict the likelihood that K.S. has the defective gene.