Supplementary Genetics Worksheet
1. What would the offspring be the genotype ratio and phenotype ratio in a cross
between a tan flower and a homozygous white flower if white is dominant?
2. What is the F2 genotype and phenotype ratio of a cross between homozygous
round and wrinkled peas if wrinkled is recessive?
3. What will be the F1 from a heterozygous tall plant and a homozygous short plant
if tall is dominant?
4. If snapdragons have incomplete dominance in flower color, what would be the
result between an orange (homozygous) and white (homozygous) parent?
5. If black color is dominant in Labrador retrievers over “off-yellow”, how could an
animal breeder determine if the male dog was homozygous or heterozygous?
6. If fruit shape of round is dominant in tomatoes over pepper-shaped, what is the
phenotype and genotype ratio of the F2 from a cross between a homozygous
round parent and a homozygous pepper-shaped plant?
7. What type of dominance would be shown in roses if a cross between two bushes
produced: 25 red, 31 yellow and 61 coral roses?
8. Describe the parents of a family of seven black and two white guinea pigs if
black is dominant.
9. Albinism is inherited as a recessive lethal (causes death) trait in many species of
corn. If a green plant has produced both green and albino offspring. What
percentage of the green offspring would you expect to carry the recessive allele
for albinism?
10. In cattle the polled (P) or hornless condition is dominant to the having horns (p).
A certain bull was mated to 3 cows; the first cow was horned and had a polled
calf; the second cow was horned and had a horned calf; the third cow was polled
and had a horned calf. Produce a pedigree chart showing the genotypes of each
animal.
11. A tomato plant of unknown genotype, but bearing spherical fruits was crossed
with one of pear-shaped fruits. This cross-resulted in 131 plants with spherical
fruits and 134 plants with pear-shaped fruits. What were the genotypes of the
parents?
12. A tomato plant that had spherical fruits was crossed with another that also had
spherical fruits. The F1 generation resulting from this cross consisted of 127
plants with spherical fruits and 41 plants with pear-shaped fruits. What were the
genotypes of the parents?
13. When a homozygous red-flowered snapdragon plant is crossed with a
homozygous white flowered plant, all of the resulting F1 generation have pink
flowers. If one of these F1 plants is self-pollinated, what fraction of the resulting
F2 plants will have red flowers and what fraction will have white?
14. In chickens, a certain gene (C) is lethal in the homozygous state. Affected
individuals die before they hatch from the egg. Heterozygous chickens (Cc) are
known as creepers because of their short, squatted appearance. Individuals
homozygous for the allele are normal.
a. If a creeper rooster were mated to normal hens, what types of
frequencies of offspring would you expect?
b. In a cross between creeper roosters and creeper hens, what proportions
of the eggs fail to hatch?
c. Does this example characterize the phenomenon of dominance or
incomplete dominance? If a lethal mutant gene were truly dominant,
what would happen to it?