Dihybrid Crosses Worksheet
1. In humans, free earlobes are controlled by the dominant allele E, and attached
earlobes by the recessive allele e. The widow’s peak hairline is regulated by the
dominant allele H, while the straight hairline is controlled by the recessive allele h.
Consider the mating of the following genotypes: EeHh X EeHh
What are the probabilities of obtaining
characteristics?
a. widow’s peak and free earlobes
F1
offspring
with
the
following
b. straight hairline and free earlobes
c. widow’s peak and attached earlobes
d. straight hairline and attached earlobes
2. What is the probability that a child from the mating of the EeHh X EeHh parents
would be a male with a widow’s peak and have attached earlobes?
3. In guinea pigs, black coat color (B) is dominant over white (b), and short hair length
(H) is dominant over long (h). Indicate the genotypes and phenotypes from the
following crosses:
a. A guinea pig that is homozygous for black and heterozygous for short hair is
crossed with a white, long-haired guinea pig.
b. A guinea pig that is heterozygous for black and for short hair is crossed with a
white, long-haired guinea pig.
c. A guinea pig that is homozygous for black and for long hair is crossed with a
guinea pig that is heterozygous for black and for short hair.
+
4. Black coat color (B) in cocker spaniels is dominant over white coat color (b). Solid
coat pattern (H) is dominant over spotted pattern (h). The gene for pattern
arrangement is located on a different chromosome than the one for color, and the
pattern gene segregates independently of the color gene. A male that is black
with a solid pattern mates with three females. The mating with female A, which is
white and solid, produces four pups: two black, solid; and two white, solid. The
mating with female B, which is black and solid, produces a single pup, which is
white, spotted. The mating with female C, which is white and spotted, produces
four pups: one white, solid; one white, spotted; one black, solid; one black, spotted.
Indicate the genotypes of the parents.