Download genetics practice problems

1. A purple-flowered pea plant is crossed with a white-flowered pea plant. All the F1
plants produce purple flowers. When the F1 plants are crossed with each other, 401
of the F2 plants have purple flowers and 131 have white flowers. What are the
genotypes of the parental and F1 generation plants?
2. In tomatoes, red fruit colour is dominant to yellow. Suppose a tomato plant
homozygous for red is crossed with one homozygous for yellow. Determine the
appearance of
(a) the F1
(b) the F2
(c) the offspring of a cross of the F1 back to the original red parent
(d) the offspring of a cross of the F1 back to the yellow parent
3. A red-fruited tomato plant, when crossed with a yellow-fruited one, produces
progeny about half of which are red-fruited and half are yellow-fruited. What are the
genotypes of the parents?
4. In guinea pigs, rough coat (R) is dominant over smooth coat (r). A rough-coated
guinea pig is bred to a smooth one, giving 8 rough and 7 smooth progeny in the F1.
a) What are the genotypes of the parents and their offspring?
b) If one of the F1 animals is mated to its rough parent, what progeny would you
expect?
5. Purple flowers are dominant to white flowers in the Jimsonweed. When a particular
purple-flowered Jimsonweed is self-pollinated, there are 28 purple-flowered and 10
white flowered progeny. What proportion of the purple-flowered progeny is truebreeding?
1. In rabbits, C=agouti coat colour, cch=chinchilla, ch=Himalayan, and c=albino. The four
alleles constitute a multiple allelic series. The agouti is dominant to the other three
alleles and albino  c is recessive to the other three alleles. Chinchilla is dominant to
Himalayan. Determine the phenotypes of progeny from the following crosses.
a)
b)
c)
d)
e)
f)
CC X cc
Ccch X Cc
Cc X Cc
Cch X chc
Cch X cc
cchch X chc
1. In humans the three alleles IA, IB, and I constitutes a multiple allelic series that
determine the ABO blood group system. For the following problems state whether
the child mentioned can actually be produced from the marriage. EXPLAIN YOUR
ANSWER.
a)
b)
c)
d)
e)
an O child from the marriage of two A individuals
an A child from the marriage of an A to a B
an AB child from the marriage of an A to an O
an O child from the marriage of an AB to an A
an A child from the marriage of an AB to a B
1. In Jimsonweed purple flower (P) is dominant to white (p), and spiny pods (S) are
dominant to smooth (s). In a cross between a Jimsonweed homozygous for white
flowers and spiny pods and one homozygous for Purple flowers and Smooth pods,
determine the following:
a)
b)
c)
d)
the phenotype of the F1
the phenotype of the F2
the progeny of a cross of the F1 back to the white, spiny parent
the progeny of a cross of the F1 back to the purple, smooth parent
2. What phenotypes would you expect to find in progeny from the following
Jimsonweed crosses?
a)
b)
c)
d)
e)
f)
PPss X ppSS
PpSS X ppss
PpSs X PpSS
PpSs X PpSs
PpSs X Ppss
PpSs X ppss
3. In summer squash white fruit (W) is dominant over yellow (w), and disk-shaped
fruit (D) is dominant over sphere-shaped fruit (d). In the following problems, the
phenotypes of the parents and their offspring are given. Determine the genotypes of
the parents in each case.
Parents
Offspring
a) White, disk X Yellow, sphere
½ White disk and ½ white sphere
b) White, sphere X White sphere
¾ White sphere and ¼ yellow sphere
c) Yellow disk X White sphere
all white disk
d) White disk X Yellow sphere
¼ White disk, ¼ White sphere,
¼ Yellow disk, ¼ Yellow sphere