Name: _________________________________
Mixed Punnett Squares
Practice Problems – Do on a separate sheet of paper
1. Coat color in mice is incompletely dominant. Yellow and white-colored mice are homozygous, while creamcolored mice are heterozygous. If two cream-colored mice mate, what phenotypic ratio (what percentages) can
we expect of their offspring? Show the Punnett Square.
2. In goats, a recessive gene causes the goats to “faint” when they are startled. A farmer breeds two goats (that
have never fainted) and their first offspring faints two days after its birth. What must the parent’s genotypes have
been? Show the cross to prove it.
3. In Andalusian fowls, black individuals (B) and white individuals (W) are homozygous. A homozygous black bird is
crossed with a homozygous white bird. The offspring are all bluish-gray. Show the cross as well as the genotypes and
phenotypes of the parents and offspring.
4. What are the genotypic and phenotypic ratios if a black individual is crossed with a bluish-gray individual? Show
the Punnett Square.
5. If two bluish-gray individuals were crossed, what would be the ratios (percentages) for both phenotype and
genotype of the offspring? Show the Punnett Square.
6. In flowers, the alleles for red petals and white petals are codominant.
a. What letter will you use to represent a red allele?
b. What letter will you use to represent a white allele?
c. What is the genotype of a red flower?
d. What is the genotype of a white flower?
e. what is the genotype of a flower that is red AND white?
7. Is it is possible for a white flower and a red/white flower to produce a red flower? Explain with a Punnett Square.
8. Multiple Allele Crosses
A. Coat color in rabbits is inherited as a series of multiple alleles. In the case of rabbits, there are four alleles
and each one is expressed with a different phenotype. Look over the summary table below:
phenotype
dark gray coat
chinchilla
Himilayan
white
allele
C
cch
ch
c
pattern of inheritance
dominant to all other alleles
dominant to Himilayan and to white
dominant to white
recessive
Suppose you cross a chinchilla rabbit (cchch) with a dark gray
rabbit (Cch). What are the possible offspring?
B. What happens when you cross a dark gray (Cc) and a white rabbit?
CHALLENGE QUESTION - If you get this right, then you are really awesome!
9. In Mendel’s pea plants, purple flower (P) color is dominant to white. Yellow seed color (Y) is dominant to green. A
plant that is homozygous for purple flower and yellow seeds is crossed with a white plant with green seeds. What is the
chance that the offspring will have purple flowers with green seeds?
HINT: use the Punnett Square provided!