Download Genetics Practice 4: Sex Linked Traits - District 279

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Genetics Practice 4: Sex linked Traits
1. Color blindness is a sex-linked recessive trait. A colorblind woman marries a man with normal vision.
What genotype and phenotype of children would be expected from such union?
2. A man sues his wife of the grounds of infidelity. Both man and wife have normal eyes, but there is a
daughter who has coloboma iridis, which is a fissure or a split of the iris of the eye. This characteristic is
known to be inherited as a sex-linked recessive. If you were the man’s lawyer could you use this as
evidence?
3. A woman with normal vision marries a man with normal vision and they have a colorblind son. Her
husband dies and she marries a colorblind man. Show the types of children that might be expected from
this marriage and the proportion of each.
4. In humans the gene for hemophiliac is sex-linked and recessive to the gene for normal blood clotting.
Determine the genotype of the parents of the following crosses and the expected phenotype and
genotype ratios for the crosses.
a. Hemophiliac woman X normal man
b. Normal heterozygous woman X Hemophiliac man
c. Normal homozygous woman X hemophiliac man
d. Normal heterozygous woman X normal man
5. Duchenne muscular dystrophy is a sex-linked recessive disorder that results in the progressive weakening
and loss of skeletal muscle. A family has 2 sons with Duchenne MD and one son that is normal. What
are the genotypes of the boys and their parents?