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Name: _________________
PUNNETTE SQUARE PROBLEMS:
#1.)
Albinism is the absence of skin pigmentation and is a recessive trait found in
humans and other animals. In the human population about 1/20,000 individuals is an
albino. Normal pigmentation (A) is dominant to albinism (a). If an albino woman marries
a homozygous normal man, what is the likelihood that one of their children will display
albinism?
KEY: ____________________________________________________________
PARENTAL GEOTYPES: ♀ ________________ ♂ ________________
POSSIBLE GAMETES (eggs and sperm):
♀____ and _____ ; ♂ _____ and _____
SET UP AND FILL IN THE PUNNETT SQUARE:
♂
PHENOTYPES: ______________________________
♀
GENOTYPES: _______________________________
ANSWER THE QUESTION: ________________________________________________________
#2.) A common squash in Texas is the Yellow crooked-neck squash. This fruit is a
source of vitamin A, B, and C. It also contains calcium and iron. Yellow colored squash
is recessive to white-colored squash. If a yellow male squash is crossed with a
heterozygous female white-squash, what are the predicted genotypes and phenotypes
of offspring?
KEY: ____________________________________________________________
PARENTAL GEOTYPES: ♀ ________________ ♂ _______________
POSSIBLE GAMETES (eggs and sperm):
♀____ and _____ ; ♂ _____ and _____
SET UP AND FILL IN THE PUNNETT SQUARE:
♂
PHENOTYPES: ______________________________
♀
GENOTYPES: _______________________________
ANSWER THE QUESTION: ________________________________________________________
Name: _________________
#3.) Polydactylous cats have more than five toes. In fact, the author, Ernest
Hemingway is credited with establishing a large colony of about 50 feral polydactylous
cats in the Florida Keys. One of his cats, Princess six-toes appeared in the New York
Times. The polydactyl allele (P) is dominant over the allele for five toes and fingers (p).
Predict the offspring of a mating between a heterozygous polydactylous male cat and a
female cat homozygous for five toes and fingers.
KEY:___________________________________________________________
PARENTAL GEOTYPES: ♀ _______________ ♂ ________________
POSSIBLE GAMETES (eggs and sperm):
♀____ and _____ ; ♂ _____ and _____
SET UP AND FILL IN THE PUNNETT SQUARE:
♂
PHENOTYPES: ______________________________
♀
GENOTYPES: _______________________________
ANSWER THE QUESTION: ________________________________________________________
#4.) Blood type in humans is controlled by 2 of 3 possible alleles. Type A & type B
blood may be inherited in a heterozygous or dominant fashion, while type O blood is
homozygous recessive & type AB blood is co-dominant that is both alleles express at
the same time. Cross a heterozygous male with a heterozygous female. What are the
phenotypic and genotypic ratios that result. Be sure to superscript the A,B, & I alleles.
KEY: _______________________________________________________
PARENTAL GEOTYPES: ♀________________ ♂ _______________
POSSIBLE GAMETES (eggs and sperm):
♀____ and _____ ; ♂ _____ and _____
SET UP AND FILL IN THE PUNNETT SQUARE:
♂
PHENOTYPES: ______________________________
GENOTYPES: _______________________________
♀
ANSWER THE QUESTION: _________________________________________