Q1. The sex linked (X linked) Xg locus in humans has two alleles, a+ abd a. The a+ allele causes the presence of Xg surface protein antigen on red blood cells, while the recessive a allele does not. The Xg locus maps 10 centimorgans from the STS locus. The recessive sts allele results in the lack of steroid sulfatase activity and homozygous females, as well as sts/Y males, develop ichthyosis, a form of scaly skin. A man with ichthyosis and no Xg antigens has a normal daughter with Xg antigens who is expecting a child.

a. If the child is a boy, what is the probability that he would lack the Xg antigen and have ichthyosis?

b. What is the possibility that the son would have both the Xg antigen and ichthyosis?

Q2. A man enters hospital complaining of chest pain. His history includes smoking, a stressful job, a diet heavy in saturated fats, lack of exercise, and high blood pressure. Although he is not suffering from a heart attack, his doctor explains to him that a heart attack is quite possible. What did the chest pain indicate? Why is the man a major candidate for a heart attack?