Genetics Practice Problems
SHOW ALL WORK!
1. Bunnies can have straight ears or floppy ears. Straight ears are dominant
(EE or Ee) and floppy ears are recessive (ee). If a straight eared bunny (EE) is
crossed with a floppy eared bunny (ee), what percentage of the offspring will
have straight ears? _____________
2. If two bunnies are both heterozygous (Ee) and are mated, what percentage of
the offspring will have floppy ears? ___________
3. If a heterozygous bunny is crossed with a floppy eared bunny, what
percentage of the offspring will have floppy ears? __________
4. Also in bunnies, brown coat color is dominant to white. If two white bunnies
are crossed, what percentage of the offspring will be white?
_________________
5. If a brown bunny (Bb) is crossed with a white bunny (bb), what percentage of
the offspring will be white? ______________
A male green parakeet breeds with a female blue parakeet. All the offspring are
green. What trait is dominant?
A heterozygous green parakeet breeds with a homozygous recessive blue parakeet.
What is the phenotype ratio of their offspring?
A homozygous dominant green parakeet breeds with a heterozygous green
parakeet. What proportion of their offspring will be green?
An apterous (wingless) male stonefly mates with a winged female stonefly. All 200
offspring are winged. After these F1 offspring mature, a male and female are mated.
What proportion of the F2 offspring will be apterous (wingless)?
A winged stonefly is captured and a researcher wants to know if it is homozygous or
heterozygous. With which kind of stonefly should a test cross be performed to find
out?
homozygous dominant winged stonefly
heterozygous winged stonefly
homozygous recessive apterous (wingless stonefly)
A purebred red flower and a purebred violet flower are crossed, with all offspring
being violet. What color is dominant?
A homozygous dominant violet flower is then crossed with a homozygous recessive
red flower. What proportion of the offspring will be red?
Yellow is the dominant color for sulfur butterflies, while white is recessive. A
heterozygous sulfur butterfly breeds with a homozygous recessive sulfur butterfly.
What is the pehonotype ratio of the offspring?
In dogs, straight ear is dominant to flop ear. You decide to adopt a stray straighteared dog. What possible genotypes might this dog be?
A heterozygous straight-eared dog breeds with a flop eared dog. Is there any
possibility of puppies with flop ears?
In dogs, straight fur is dominant to curly fur. A homozygous recessive ear,
heterozygous fur dog breeds with a heterozygous ear, homozygous recessive fur
dog. What proportion of the offspring will be flop-eared and curly-furred?
In cats, extra toes is dominant to five toes and long tails are dominant to stub tails. A
heterozygous six-toed, heterozygous long-tailed cat breeds with a five-toed, stubtailed cat. What proportion of kittens will have five toes and long tails?
Challenge Questions
Of 100 white cats, 48 have long whiskers and 52 have short whiskers. Of 100
colored cats, 54 have long whiskers and 46 have short whiskers. Are the genes for
fur color and whisker length linked?
In a series of pigeon matings the following results were obtained:
P adults
F1 offspring
mottled x mottled: 4 mottled
2 grey
2 white
mottled x white:
4 mottled
4 white
mottled x grey:
4 mottled
4 grey
grey x grey:
8 grey
white x white:
8 white
What pattern of inheritance does the mottled trait follow?
Fur color in mice can be black, agouti (brown), yellow. Data from many controlled
breedings is listed below:
P adults
F1 offspring
F2 offspring
black x agouti:
100% black
75% black
25% agouti
agouti x yellow:
50% yellow 50% agouti
agouti x agouti
:
100% agouti
black x black:
100% black
yellow x yellow:
67% yellow 33% agouti
black x yellow:
100% black
83% black
17% agouti
What is the order of dominance for fur color?
What can explain the pattern of inheritance for yellow fur?
Examine pedigree B above. How is the trait inherited?
What is the genotype of the following individuals?
I-1
I-2
I-3
I-4
II-1
II-2
II-3
II-4
Short “essay”
The ferocious Jackalope (pictured at right) is a hybrid of a jackrabbit and
an antelope. Jackalopes may be either long horned or short horned. The
following data was obtained through controlled matings.
F1 Progeny
P1 cross
# long horn
# short horn
(a) long horn x long
39
2
horn
(b) long horn x short
42
0
horn
(c) short horn x short
0
40
horn
How are the long and short horn traits inherited?
Predict the results of the F1 x F1 mating from cross (b)
What are the possible explanations for the 2 short horned jackalopes
from cross (a)?