Genetics - Sex-Linked Crosses
1. Can a male be homozygous for a sex-linked character? From which parent does a male receive his sex-linked genes? To which sex among his offspring does he transmit his sex-linked characters? If a gene were located on his Y chromosome, to what offspring would he transmit it?
2. Color-blindness is a sex-linked recessive character, and sex in man is determined essentially as in Drosophila. A girl of normal vision whose father was color-blind marries a color-blind man. What will be the nature of their children?
3. A woman of normal vision, whose father was color-blind marries a man of normal vision whose maternal grandfather was color-blind. What type of vision will be expected in their children?
4. A color-blind boy's parents and grandparents all had normal vision. What was the genotype of his maternal grandmother? Of his mother?
5. Yellow body (g) in Drosophila is a sex-linked character recessive to gray body (G). A certain gray female mated with an unknown male produced some yellow and some gray offspring of both sexes. What was the genotype of the original female? What was the phenotype of the male to which she was mated?
6. A female fruit fly with a sable body (s) is mated with a male having gray body (S). Their daughters are gray, their sons sable. In what chromosomes are the genes S and s?
7. Hemophilia is a sex-linked blood disorder. A woman whose maternal grandfather suffered from hemophilia has parents that are normal. The woman's husband is normal. She has a hemophilic son. What is the chance that her next son will be normal? Will any of her daughters have hemophilia? Will any be carriers?
8. An albino (non-sex-linked) non-hemophilic man marries a normally-pigmented, non-hemophilic woman whose father was hemophilic and whose mother was albino. What kinds of children can they have and in what proportions?
9. Two normal-visioned parents produce a color-blind son. What are the genotypes of the parents? What are the chances of their next child being a color-blind daughter?
10. In human beings, migraine (a type of headache) is due to a dominant factor. A normal-visioned woman who has never suffered from migraine takes her daughter to a doctor for examination. In the course of the examination the doctor discovers that the girl is color-blind, and suffers from migraine. What does the doctor automatically know about the father?
11. In man, aniridia (a type of blindness) is due to a non-sex linked dominant factor. Optic atrophy (another type of blindness) is due to a sex-linked recessive factor. A man blind from optic atrophy marries a woman blind from aniridia. Assuming that the mother is homozygous for both characters, would any of their children be expected to be blind? Which type of blindness would they have?
12. A non-hemophilic man who is blind from aniridia, but whose mother was not blind, marries a non-hemophilic woman who is not blind, but whose father was hemophilic. If they have four sons, what combinations of these traits would they most probably have?