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Practice Sex-linked and Sex Influenced Problems
NAME ______________________________
1. In cats, coat color is controlled by a codominant, sex-linked gene. Calico cats have
both orange an black splotches on their white coat. Show the cross between an
orange splotched male and a calico female.
2. Hemophilia is a sex-linked trait. A person with hemophilia is lacking certain proteins
that are necessary for normal blood clotting. Hemophilia is caused by a recessive
allele so use N for “normal” and n for hemophilia. Since hemophilia is sex-linked,
remember a woman will hav two alleles (NN or Nn or nn) but a man will only have
one allele (N or n). A woman who is heterozygous (a carrier) for hemophilia marries
a normal man:
a. What are the genotypes of the parents?:
b. Make a Punnett square for the above cross.
3. Can a colorblind female have a son that has normal vision? Colorblindness is casued
by a sex-linked recessive allele.
* use N= normal vision and n= colorblind
4. Baldness is a sex-influence autosomal trait. What parental genotypes could produce a
bald woman? * use B= bald and b= hair.
5. What is the probability of getting a bald female from a bald man and a heterozygous
female with hair? (Baldness is dominant)
6. If a man becomes bald and his father is not bald, what are the possible genotype(s) of
the mother?
7. If a woman’s parents are not bald, she is not bald, and her husband and older daughter
are both homozygous bald, then what is the genotype of both the woman and her
parents?
8. What is the probability that the woman and her husband would have the bald
daughter?