1. (8 points) Anhydrotic ectodermal dysplasia is an X-linked
recessive disease in cattle, causing tooth abnormalities and
hairlessness. Arachnomelia is an autosomal recessive condition that
causes spider legs in newborn calves. Use ‘D’ to indicate the
dominant, normal teeth and hair in cattle and ‘d’ for the
dysplasia. Use ‘L’ for normal legs and ‘l’ for spider legs. Suppose
a heifer having normal teeth and hair and normal legs but whose
sire had dysplasia and spider legs is backcrossed to her sire.

a. What are their genotypes?

b. What are the genotypes, phenotypes, and genotypic and
phenotypic proportions we expect in their progeny?

2. (6 points) In German Shepherds, hemophilia A is an X-linked
recessive disease, affecting the blood clotting times in dogs
having the disease. Use ‘+’ to indicate the normal, normal blood
clotting time allele and ‘a’ for the hemophilia allele. A bitch
(female) who has normal blood clotting times and whose sire (male)
had hemophilia A is mated with a sire with normal blood clotting
times but whose sire also had hemophilia A.

a. What are the genotypes of the 4 dogs described in the
problem?

b. What are the genotypes, phenotypes, genotypic and phenotypic
proportions you would expect to observe in the puppies produced
from this cross?

3. (8 points) In turkeys, inhibited feathering is a sex-linked
dominant gene (F). Use ‘f’ to denote the normal feathering allele.
Suppose a bald hen (female) is crossed with a normally feathered
rooster.

a. What are the genotypes of the two birds described?
b. What are the genotypes, phenotypes, genotypic and phenotypic
proportions expected in the F1 progeny? c. What will be the
genotypes, phenotypes and proportions produced when the F1 males
are backcrossed?

4. (8 points) In guinea pigs, short hair (H) is dominant to long
hair (h) and the heterozygous condition when you cross a yellow
coat (CY) and white coat (CW) gives you a cream coat. These two
loci are located on different chromosomes. A heterozygous
short-haired cream guinea pig is crossed to a long-haired white
guinea pig.

a. What are the genotypes, phenotypes and proportions of the
pups (baby guinea pigs) produced?

b. What are the genotypes, phenotypes and proportions expected
if we crossed the heterozygous short- haired cream guinea pig with
a heterozygous short-haired yellow guinea pig?