1. In guinea pigs, short hair is dominant to long hair. Also in guinea pigs, black eyes are dominant to
red eyes. A male guinea pig that is heterozygous for both traits is crossed with a female that is long
haired and red eyed. What are the expected phenotypes of their offspring and in what proportion?
PHENOTYPES:
2. If both parents are heterozygous for both traits, what are the expected phenotypes of their
offspring and in what proportion?
PHENOTYPES:
3. In horses, trotter (T) is dominant over pacer (t). Straight manes (H) are dominant over curly
manes. (h). A curly maned pacer horse is mated to one who is homozygous dominant for both
traits. What would you expect their offspring to look like?
4. If you have two horses that are both heterozygous for both traits – trotting and mane. What ratio of
the offspring would you expect to be curly maned and a pacer?
PHENOTYPES:
5. SpongeBob loves growing flowers for his pal Sandy! Her favorite flowers, Poofkins, are found in red, blue,
and purple. Use the information provided and your knowledge of incomplete dominance to complete each
section below. Write the correct genotype for each color if R represents a red gene and B represents a blue gene.
Red - _____ Blue - ______ Purple - _____
1. What would happen if SpongeBob crossed a Poofkin with red flowers with a Poofkin with blue flowers?
Complete the Punnett square to determine the chances of each flower color.
(a) Give the genotypes and phenotypes for the offspring.
(b) How many of the plants would have red flowers? _____%
(c) How many of the plants would have purple flowers? _____ %
(d) How many of the plants would have blue flowers? _____ %
Sex-linked Traits Directions: Complete the following problems by doing the punnett square for each cross and
answering the question asked.
6. Complete a punnett square for the cross between a human female (XX) and a human male (XY). What is the
chance that the parents will have a girl?
7. If the same parents have four boys, what is the probability their fifth child will be a girl?
8. Hemophilia is a recessive sex-linked disease carried on the X chromosome in humans. A woman who is a
carrier for hemophilia marries a normal male. What are the possible phenotypes of their children?
9. A woman who is a carrier for hemophilia marries a man with hemophilia. Could any of their children have
hemophilia? If so, would the child be male or female?
10. A woman with hemophilia marries a man who does not have hemophilia. What are the possible phenotypes
of their children?
11. A woman without hemophilia marries a man with hemophilia. They have a daughter with hemophilia. What
is the genotype of the mother and father?
12. Colorblindness is a sex-linked recessive trait in humans. A colorblind man marries a female who is a carrier
for colorblindness. What is the probability that they will have a child who is colorblind?
13. A colorblind male marries a female who is not colorblind (homozygous). What are the possible phenotypes
of their children?