Genetics Problems (10 points)
Show your work!
1. In cats, the Manx allele (M) causes a stubbed tail, while the recessive allele
(m) confers a long tail. Cats of genotype MM die as embryos. If two Manx cats
mate and six kittens are born, how many would you expect to have a long
tail?
2. Mr. Spock’s father came from the planet Vulcan, and his mother came from
planet Earth. A Vulcan has pointed ears and a heart located on the right side
of the chest. Mr. Spock has both of these traits. Vulcans and Earthlings have
many genes in common, including the genes for ear shape and heart location,
each of which has two alleles. Mr. Spock married an Earth woman and they
had many children. About half of the children have pointed ears and hearts
on the right side, like Spock, and about half have rounded ears and hearts on
the left side, like their mother. Explain the inheritance pattern for ear shape
and heart location.
3. In Klingons, one gene determines hair texture and another gene determines
whether the individual will have a sagittal crest (a prominent forehead
protrusion). The two genes are not linked. The allele for curly Klingon hair
(K) is dominant to the allele for silky Earthling hair (k). The allele for a
sagittal crest (S) is dominant to the allele for a smooth forehead (s). Kayless
is half-human, half-Klingon with the genotype KkSs. He mates with Sara, also
a heterozyote for both genes. If they had 16 children, what would be the
expected phenotypic ratio of the children?
4. Two mothers give birth to sons at the same time in a busy hospital. The son
of couple 1 is afflicted with hemophilia A, which is a recessive sex-linked
disease. Neither parent has the disease. Couple 2 has a normal son even
though the father has hemophilia A. The two couples sue the hospital in court,
claiming that a careless staff member switched the babies at birth. You
appear in court as an expert witness for the hospital. You explain that
without more information it is impossible to determine if the babies were
switched at birth. Provide your explanation below.
5. The following pedigree is for a human trait called osteopetrosis, which is
characterized by bone fragility and dental abscesses. Explain the inheritance
pattern for this disorder.