Name: _________________________________________ Period: _____ Date: __________
Genetics Practice Problems
1. In pea plants, tall (T) is dominant to dwarf (t). Show the cross between a
heterozygous tall and a dwarf homozygous plant. Use the Punnett square to
predict the % Phenotype and Genotype of the offspring.
% Genotype
% Phenotype
Homozygous = _____
Tall = _____
Heterozygous = ______
Dwarf = _____
2. Show the cross between two heterozygous (Tt) tall plants. Use the Punnett
square to predict the % Phenotype and Genotype of the offspring.
% Genotype
% Phenotype
Homozygous = _____
Tall = _____
Heterozygous = ______
Dwarf = _____
3. In pea plants, green pods are dominant to yellow pods. Show the cross
between a homozygous yellow pod plant (gg) and a hybrid green pod plant
(Gg)? Use the Punnett square to predict the % Phenotype and Genotype of the
offspring.
% Genotype
% Phenotype
Homozygous = _____
Green = _____
Heterozygous = ______
Yellow = _____
4. If two green pod plants (Gg) are crossed what are the expected phenotypes
of the offspring and genotypes of the offspring? Use the Punnett square to
predict the % Phenotype and Genotype of the offspring.
% Genotype
% Phenotype
Homozygous = _____
Green = _____
Heterozygous = ______
Yellow = _____
5. In humans, tongue rolling is a dominant trait; those with the recessive
condition cannot roll their tongues? If two people one is a hybrid (Rr) to roll
tongue and one is a pure recessive (rr) to roll tongue what percent of the
offspring could roll there tongue?
% can roll tongue __________
6. In purple people eaters, one-horn is dominant (H) and no horns are recessive
(h). Use the Punnet Square showing the cross of a purple people eater that is
hybrid for horns (Hh) with a purple people eater that does not have horns (hh).
Summarize the genotypes & phenotypes of the possible offspring
% Genotype
% Phenotype
Homozygous = _____
Horn = _____
Heterozygous = _____
No Horn = _____
Incomplete Dominance Problems
7. In shorthorn cattle, when a red bull (RR) is crossed with a white cow (WW),
all the offspring are roan (RW)—a spotted, [4]
a. What offspring are expected from mating a roan bull
and a roan cow?
b. What phenotypes would you expect from a cross
between a red bull and a white cow?
Roan _______%
Red _______%
White_______%
8. In some chickens, the gene for feather color is controlled by incomplete
dominance. The allele for black is BB and the allele for white is WW. The
heterozygous phenotype is known as erminette (RW) (black and white
spotted). [3]
a. What is the genotype for black chickens? _______
b. What is the genotype for white chickens? _______
c. What is the genotype for erminette chickens? _______
9. If two erminette chickens were crossed, what is the probability that: [4]
a. They would have a black chick? ______%
b. They would have a white chick? ______%
c. They would have a erminette chicks? ______%
10. A black chicken and a white chicken are crossed. What is the probability
that they will have erminette chicks? ____% [2]
11. In snapdragons, flower color is controlled by incomplete dominance. The
two alleles are red (RR)and white (WW). The heterozygous genotype is
expressed as pink (RW). [4]
a. A pink-flowered plant (RW) is crossed with a whiteflowered plant (WW). What is the probability of producing
pink-flowered plant? _______%
red-flowered plant? _______%
white-flowered plant? _______%
12. In Andalusian fowls, black individuals (BB) and white individuals (WW) 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]
a.
Phenotype
Black ______% White _____% Bluish-gray ______%
b.
Genotype
BB _______%
WW _______%
RW _______%
13. What results if two bluish-gray individual are crossed? Show the cross as
well as the genotypes and phenotypes of the parents and offspring. [4]
a.
Phenotype
Black ______% White _____% Bluish-gray ______%
b.
Genotype
BB _______%
WW _______%
RW _______%