Download Genetics Practice Problems - Part 2 - Parkway C-2

Honors Biology II – Genetics Practice Problems
Instructions – Try to solve these problems without the use of a Punnett square. Of course, you
may use a Punnett square if you’d like but it may be easier to solve many of these problems
using the probability rules that we have discussed in class.
Part II
1. In maize, a dominant allele A is necessary for seed color as opposed to colorless (a).
Another gene has a recessive allele wx that results in waxy starch as opposed to normal
starch (Wx). The two genes segregate independently.
a. What does the phrase “The two genes segregate independently” mean?
b. Give phenotypes and relative frequencies (i.e. percentages) for the offspring
resulting when a plant with the AaWxWx genotype is crossed with a plant with the
aawxwx genotype.
2. In guinea pigs rough coat (R) is dominant over smooth coat (r). A roughcoated guinea pig is bred to a smooth one, giving eight rough and seven
smooth baby guinea pigs in the F1 generation.
a. What are the genotypes of the parents and their offspring?
b. If one of the rough F1 animals is mated to its rough parent
(Guincest?), what offspring would you expect?
3. Two black female mice are crossed with same brown male. In a number of litters female
X produced 9 blacks and 7 browns and female Y produced 14 blacks.
a. What is the mechanism of inheritance of black and brown coat color in mice?
b. What are the genotypes of the parents?
4. Genes A, B, and C assort independently and are dominant to their respective alleles a, b,
and c. Two triply heterozygous individuals are crossed.
a. What is the probability that a given offspring will be phenotypically ABC, that is, will
exhibit all three dominant traits?
b. What is the probability that a given offspring will be genotypically homozygous for
all three dominant alleles?
c. What is the probability that a given offspring will be genotypically homozygous for
all three recessive alleles?