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Name: _________________________________ Date: __________________ Class: _______
POLYHYBRID EXTRA CREDIT #1 (Pea Plants)
In order to earn ANY extra credit for any of the problems below, you must write clearly,
number each problem, show ALL of your work, and circle your answers. You must also
staple all of your answers (with your name on it) to the BACK of this sheet, and fill out
your name, date and class on the top of this paper.
Garden pea plants, Pisium Sativumi, are studied with regard to three independently assorting
loci that control pod color (the allele for green, Y, is dominant to the allele for yellow, y), seed
shape (the allele for round, W, is dominant to the allele for wrinkled, w), and pod shape (the
allele for full, C, is dominant to the allele for constricted, c). Two plants, each heterozygous at all
three loci, are crossed.
1. Identify the genotypes of each parent
2. Identify each of the gametes produced by each parent and the expected proportion of
each.
3. What proportion of the progeny (offspring) would be expected to be phenotypically
dominant for all three traits?
4. Refer back to the pea-plant cross described above. What proportion of the progeny would
be expected…
a. To be homozygous recessive for all three traits?
b. To be heterozygous at all three loci?
c. To have the genotype YYWwcc?
d. To have the genotype yyWWcc?
Name: _________________________________ Date: __________________ Class: _______
POLYHYBRID EXTRA CREDIT #2 (Rabbits)
In order to earn any extra credit for any of the problems below, you must write clearly,
number each problem, show ALL of your work, and circle your answers. You must also
staple all of your answers (with your name on it) to the BACK of this sheet, and fill out
your name, date and class on the top of this paper.
In rabbits, the allele for spotted coat, S, is dominant to the allele for solid, s. The allele for black
coat color, B is dominant to the allele for brown, b. The genes for these two traits are carried on
different pairs of autosomes.
1. All of the progeny (offspring) produced by mating a solid, black rabbit with a spotted,
brown rabbit were found to be spotted, black. What are the genotypes of these parents?
2. What are the genotypes of the offspring?
The allele for brown eyes, E, is dominant to the allele for red eyes, r. Two rabbits, each
heterozygous at all three loci, are crossed.
3. Identify the genotypes of each parent
4. What proportion of the progeny (offspring) would be expected to be phenotypically
recessive for all three traits?
5. Refer back to the rabbit cross described above. What proportion of the progeny would be
expected…
6. To be heterozygous at all three loci?
7. To have the genotype SSbbEe?
8. To have the genotype SsBBee?
Name: _________________________________ Date: __________________ Class: _______
POLYHYBRID EXTRA CREDIT #3 (Goldfish)
In order to earn ANY extra credit for any of the problems below, you must write clearly,
number each problem, show ALL of your work, and circle your answers. You must also
staple all of your answers (with your name on it) to the BACK of this sheet, and fill out
your name, date and class on the top of this paper.
Assume with goldfish size that large (S) is dominant to small (s), orange body color (C) is
dominant to yellow body color (c) and sharp teeth (T) are dominant to dull teeth (t). The genes
for these two traits are carried on different pairs of autosomes. Two fish, one heterozygous at all
three loci, is crossed with one that is heterozygous for size and color, but homozygous for dull
teeth.
1. Identify the genotypes of each parent
2. Identify each of the gametes produced by each parent and the expected proportion of
each.
3. What proportion of the progeny (offspring) would be expected to be phenotypically
dominant for all three traits?
4. Refer back to the goldfish cross described above. What proportion of the progeny
(offspring) would be expected…
a. To be homozygous recessive for all three traits?
b. To be heterozygous at all three loci?
c. To have the genotype SsccTT?
d. To have the genotype SSCctt?
Name: _________________________________ Date: __________________ Class: _______
POLYHYBRID EXTRA CREDIT #4 (Squash)
In order to earn ANY extra credit for any of the problems below, you must write clearly,
number each problem, show ALL of your work, and circle your answers. You must also
staple all of your answers (with your name on it) to the BACK of this sheet, and fill out
your name, date and class on the top of this paper.
The weight of the fruit in one variety of squash is determined by three pairs of genes. The
homozygous dominant condition AABBCC, results in 6-pound squashes, and the homozygous
recessive condition, aabbcc, results in 3-pound squashes. Each dominant gene adds ½ pound
to the minimum 3-pound weight. When a plant having 6-pound squashes is crossed with one
having 3-pound squashes, all the offspring have 4 ½ pound fruit.
1. What would be the weights of the F2 fruit, if two of these F1 plants were crossed?
2. What would be the chance of producing 4 ½ pound squashes if these two plants were
crossed: AaBBCc x AaBbcc
3. What would be the chance of producing 3 pound squashes if these two plants were
crossed: aaBbCc x AabbCc
4. List all the possible genotypes for a squash that weighs 5 pounds.
5. List all the possible genotypes for a squash that weighs 4 ½ pounds.