Download Practice Crosses

Cross Practice Problems
Show Punnett square and give Genotype and Phenotypes for each
cross
In humans, brown eyes are dominant over blue eyes. What
type of offspring would you expect if you crossed a
heterozygous brown eyed person with a heterozygous
brown eyed person?
In humans, tongue rolling is dominant to non-tongue
rolling. What would be the expected type of offspring if
Beyonce (homozygous for tongue rolling) and Jay-Z
(heterozygous) had another child?
In garden peas, round peas are dominant to wrinkled peas.
If you crossed homozygous dominant and homozygous
recessive pea plants, what would be the genotype and
phenotype of the offspring?
In pea plants, purple flowers are dominant to white
flowers. What parental genotypes would produce offspring
that are all heterozygous for the purple trait?
If out of 100 offspring, 74 are purple flowered and
26 are white, what were the probably genotypes
and phenotypes of the parents?
Two short-haired guinea pigs are mated several times. Out
of 100 offspring, 50 of them have long hair (recessive).
What are the probable genotypes of the parents?
In goats, a recessive gene causes the goats to “faint” when they’re
startled. A farmer breeds two goats that have never fainted and their
offspring faints two days after its birth. What must the parents’
genotypes have been? Show the cross to prove it.
A tall plant of unknown genotype is test-crossed (crossed with a
recessive plant). Of the offspring, 869 are dwarf and 912 are tall. What
is the genotype of the unknown parent? Show the cross to prove it.
Two pea plants are heterozygous for both seed shape
(round is dominant) and seed color (yellow is dominant).
What are the possible genotypes and phenotypes for these
two traits when these plants are crossed?
About 70% of Americans perceive a bitter taste from the chemical
phenylthiocarbamide (PTC). The ability to taste PTC results from a
dominant allele. Albinism is also a single locus trait with normal
pigmentation being dominant. A normally pigmented woman who
cannot taste PTC has a father who is an albino taster. She marries a
homozygous, normally pigmented man who is a taster, but who has a
mother that does not taste PTC. What are the genotypes and
phenotypes of the possible children?