Download Biology 621 Practice Problems in Mendelian Genetics

Biology 621
Practice Problems in Mendelian Genetics
You must show all your work for these problems. This means 1) show the gametes formed 2)
place the gametes one the outside of the Punnett square 3) solve the Punnett square, 4) answer
the question.
I.
Problems Involving One Gene
1.
In cats, long hair is recessive to short hair. A true-breeding (homozygous) short-haired
male is mated to a long-haired female. What will their kittens look like?
2.
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?
3.
In cattle, there is an allele called dwarf which, in the heterozygote, produces calves with
legs which are shorter than normal. This is a homozygous lethal (the homozygous dwarf
calves spontaneously abort early or a stillborn). If a dwarf bull is mated to 400 dwarf
cows, what phenotypic ratio to you expect among the living offspring?
II.
Problems Involving Two Genes
4.
In cats black color is dominant to a special, temperature-sensitive albino gene which
produces cats with dark legs, faces and tails (Siamese cats). A short haired (dominant)
Siamese colored female is bred to a long-haired black male. They have eight kittens: 2
black, short-haired; 2 black, long-haired; 2 Siamese, short-haired; and 2 Siamese, longhaired. What were the genotypes of the two parents?
5.
In garden peas, long stems are dominant to short stems, and yellow seeds are dominant to
green seeds. 100 long/yellow pea plants, all of which had one short/green parent, are
interbred (bred to each other). 1600 progeny (offspring) result. Please answer the
following questions about these progeny.
a. Assuming that these two genes are unlinked, about how many long/green pea
plants would you expect to find among the offspring?
b. What ratio of yellow to green seed color would you expect among the offspring?
c. What would you expect the overall phenotypic ratio among the 1600 offspring to
be (taking into consideration both traits)
6.
In mice, black fur is dominant to white fur, and long tails are dominant to short tails. A
long-tailed black male mouse is crossed with a short-tailed white female mouse, and nine
offspring are produced. Five are black with long tails, and four are black with short tails.
What is the genotype of the male mouse?