Posted: September 13th, 2017

1. Two cats are mated. One of the parent cats is long-haired (recessive allele). The litter which results contains two short-haired and three long-haired kittens. What does the second parent look like, and what is its genotype?

1.  Two cats are mated. One of the parent cats is long-haired (recessive allele). The litter which results contains two short-haired and three long-haired kittens. What does the second parent look like, and what is its genotype?

2.  Mr. and Mrs. Jones have six children. Three of them have attached earlobes (recessive) like their father, and the other three have free earlobes like their mother. What are the genotypes of Mr. and Mrs. Jones and of their numerous offspring?

3.  Mr. and Mrs. Anderson both have tightly curled hair. (The hair form gene shows incomplete dominance. There are two alleles, curly and straight. The heterozygote has wavy hair.) The Andersons have a child with wavy hair. Mr. Anderson accuses Mrs. Anderson of being unfaithful to him. Is he necessarily justified? Why or why not?

4.  In certain portions of the Jewish population, there is a genetic disease called Tay Sachs disease, which is fatal to infants within the first five years of life. This disease is caused by a recessive allele of a single gene. Why does this disease persist, even though it is invariably fatal long before the afflicted individual reaches reproductive age? (In other words, why doesn’t the allele for Tay Sachs disease simply disappear?)

5.  Elizabeth is married to John, and they have four children. Elizabeth has a straight nose (recessive) and is able to roll her tongue (dominant). John is also able to roll his tongue, but he has a convex (Roman) nose (dominant). Of their four children, Ellen is just like her father, and Dan is just like his mother. The other children — Anne, who has a convex nose, and Peter, who has a straight nose — are unable to roll their tongues. Please answer the following questions about this family.
•    What are the genotypes of Elizabeth and John?
•    Elizabeth’s father was a straight-nosed roller, while her mother was a convex-nosed non-roller. What can you figure out about their genotypes?
•    John’s father was a straight-nosed roller, while his mother was a convex-nosed roller. What can you determine about their genotypes?

6.  Earl has normal color vision, while his wife Erma is colorblind.  Colorblindness is an X-linked trait, and the normal allele is dominant to the colorblindness allele. If they have a large family, in what ways should the colorblindness trait affect their children?

7.  In cats, there is a coat color gene located on the X chromosome. This gene has two alleles—orange and black. A heterozygous cat has tortoiseshell color (a splotchy mixture of orange and black). Predict the genotypic and phenotypic frequencies among the offspring of the following crosses. Pay careful attention to the genders of the offspring.
•    Black female X Orange male
•    Orange female X Black male
•    Tortoiseshell female X Black male
•    Tortoiseshell female X Orange male

8.  In a case in Spokane, Washington, a young woman accused a soldier of being the father of her child. The soldier, of course, denied it. The soldier’s lawyer demanded that blood types be taken to prove the innocence of his client. The following results were obtained: Alleged father – Type O;  Mother – Type A;  Child – Type AB. The court found the soldier guilty on the basis of the woman’s remarkable memory for dates and details that apparently eliminated all other possible fathers.
•    What are the possible genotypes for these three people?
•    Do you agree with the court’s decision? Why or why not?