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Monohybrid Cross Practice
1. A blue eyed man and a heterozygous brown eyed woman have a baby. What is the chance that the
baby will have blue eyes? Use “b” for blue and “B” for brown. Brown is dominant.
2. In fruit flies, long wings are dominant to short wings. Use “W” for long and “w” for short. What
would be the result of a heterozygous long winged fly and homozygous long winged fly cross?
3. In pea plants, round seeds (S) are dominant to wrinkled seeds (s). In a genetic cross of two plants
that are heterozygous for the seed shape trait, what fraction of the offspring should have spherical
seeds?
4. In pea plants, purple flowers are dominant to white flowers. What would be the result of a cross
between a homozygous white flowered plant and a homozygous purple flowered plant?
5. The ability to roll the tongue is dominant over the inability to roll the tongue in humans. If two
heterozygous tongue-rollers have children, what genotypes could their children have?
6. In elves, magical abilities are dominant to no magical abilities. If a heterozygous elf has a child
with an unmagical elf, what are the possible genotypes of the baby elves? What are the possible
phenotypes of the baby elves?
7. In guinea pigs, rough hair is dominant and smooth hair is recessive. If a heterozygous rough
haired guinea pig is crossed with a smooth hair guinea pig, what will the chance be that the baby
guinea pig has smooth hair? What is the chance that the baby guinea pig will have rough hair?
8. In dogs, there is a hereditary deafness caused by a recessive gene “d.” A kennel owner has a male
dog that she wants to use for breeding purposes if possible. The dog can hear, so the owner knows
his genotype is either DD or Dd. If the dog’s genotype is Dd, the owner does not wish to use him for
breeding so that the deafness gene will not be passed on. This can be tested by breeding the dog to
a deaf female (dd). In each case, what percentage of the offspring would be expected to be hearing?
What percent deaf? How could you tell the genotype of this male dog? Also, using Punnett
square(s), show how two hearing dogs could produce deaf offspring.
9. In monsters, fangs are dominant to no fangs. If two fanged monsters are crossed, and ¾ of the
offspring have fangs, and ¼ of the offspring do not, what is the genotype of the parent monsters?
10. In unicorns, straight horns are dominant to curly horns. What would be the possible genotypes of
the parents if all of the offspring have straight horns?
Dihybrid Cross Practice
1. In guinea pigs, black coat color is dominant to white coat color. Rough coat is dominant to smooth
coat. If you cross a heterozygous black, homozygous rough guinea pig with a homozygous white,
smooth guinea pig, what will be the percentages of the phenotypes of the offspring?
2. In flibbit bugs, silver wings are dominant to gold wings and large eyes are dominant to small eyes.
If a homozygous silver winged, heterozygous larged eyed bug is crossed with a homozygous silver
winged, homozygous small eyed bug, what is the chance that the offspring will have silver wings and
small eyes?
3. In polka dot plants, blue polka dots are dominant to pink polka dots. Plaid leaves are recessive to
striped leaves. If you cross a pink polka dot plant with plaid leaves with a homozygous blue polka dot
plant with homozygous striped leaves, what would be the result? If you cross two plants from the F1
generation, what will be the result?
4. In humans, brown eyes are dominant to blue eyes, and brown hair is dominant to blonde hair. If a
brown eyed, blonde haired man and a blue eyed, blonde haired woman have a baby, what is the
probability that the baby will have blue eyes and blonde hair. Be careful! Think!