Download Genetics Problem Sets

200 Genetics Problem Set #1
Punnett Square and Monohybrid Cross
SpongeBob Genetics
1. Determine the phenotype for each genotype using the information about SpongeBob.
Yellow body color is dominant to blue.
Let ______________ = yellow
YY ________
____________________ = blue
Yy _________
yy __________
Square shape is dominant to round.
Let ______________ = Square
SS ________
Ss ________
____________________ = round
ss __________
2. For each genotype, give the genotype(s) that is/are possible for Patrick.
A tall head (T) is dominant to short (t)
Tall _______________
Short __________________
Stubby Appendages (A) is dominant to lean appendages (a)
Stubby ______________
Lean __________________
3. SpongeBob SquarePants recently met SpongeSusie Roundpants at a dance. SpongeBob is
heterozygous for his squareshape, but SpongeSusie is round. Create a Punnett Square to
show the possibilies that would result is SpongeBob and SpongeSusie had children.
The possible genotypes of offspringThe possible phenotypes of offspringWhat are the chances of having a square shape child? ___ out of ____ or ______%
What are the chances of having a round shape child? ___ out of ____ or ______%
4. Everyone in Squidward’s family has light blue skin, which is the dominant trait for body
color in his hometown of Squid Valley. His family brags that they are a purebred line. He
recently married a nice girl who has light green skin, which is a recessive trait. Create a
Punnett Square to show the possibilities that would result if Squidward and his new bride
had children. Use B to represent the dominant gene and b to represent the recessive
gene.
The possible genotypes of offspringThe possible phenotypes of offspringWhat are the chances of having a light blue child? ___ out of ____ or ______%
What are the chances of having a light green child? ___ out of ____ or ______%
Would Squidward’s children still be considered purebreds? Explain your answer.
Family Guy Genetics
1. Use the information for Brian’s traits to write the phenotype for each item.
Trait
Dominant Gene Recessive Gene
Nose Color
Brown (B)
Black (b)
Ear Length
Short (L)
Long (l)
Walking
Four Legs (F) Two Legs (f)
Communication
Talking (T)
a. BB ____________
b. Tt ____________
c. ff ______________
d. tt _____________
e. Ll _____________
f. Bb _____________
g. TT _____________
h. FF _______________
Barking (t)
2. Use the information from the chart above to write genotype (or genotypes) for each trait
below.
a. Short Ears ___________
e. Walks on Two Legs ____________
b. Talks _______________
f. Black Nose ___________________
c. Long Ears ___________
g. Walks of Four Legs ____________
d. Brown Nose __________
h. Barks _______________________
3. Determine the genotypes for each using information in the chart above.
a.
b.
c.
d.
Heterozygous Talking _______________
Purebred Four Leg Walker ___________
Hybrid Short Ears __________________
Homozygous Black Nose _____________
Basic Crosses
The Punnett square is a chart used to predict the chances of an offspring receiving a
particular trait. It will not tell you how many offspring will be produced, or the order in
which they will be born.
A husband who is homozygous dominant for brown hair (BB) has a wife who is
homozygous recessive for blonde hair (bb). The allele for brown hair (B) is dominant to the
allele for blonde hair (b). Use the Punnett square below to predict the probability that they
will have offspring with brown or blonde hair.
Gametes
B
b
b
B
1. What are the chances of the offspring having blonde hair?
2. What are the chances of the offspring having brown hair?
3. What is the genotypic ratio?
4. What is the phenotypic ratio?
Now, assume both husband and wife are both heterozygous for brown hair. Use the Punnett
square below to predict the genotypes and phenotypes of their offspring.
Gametes
B
B
b
b
5. What are the chances of the offspring having blonde hair?
6. What are the chances of the offspring having brown hair?
7. What is the genotypic ratio?
8. What is the phenotypic ratio?
9. What is the dominant gene?
10.
Is there a heterozygous blonde offspring?
Why?
If curly hair is dominant to straight hair, what letters will you use to represent these genes?
11.
If a heterozygous curly-haired male marries a straight-haired female, how would
you write their genotypes? _________x ___________
12.
What would the possible gametes be for the male parent?
13.
What would the possible gametes be for the female parent?
Use the Punnett square to work out the cross and then answer the questions.
Gametes
14.
What are the chances of the offspring being homozygous curly-haired?
15.
What are the chances of the offspring having straight hair?
16.
What are the chances of the offspring being heterozygous curly-haired?
17.
What is the genotypic ratio?
18.
What is the phenotypic ratio?
Monohybrid Cross
In fruit flies, Long wing (L) is dominant to short wing (l).
Predict the outcome of the following monohybrid crosses. Give the (1) Parental genotypes;
(2) Genotypic Ratio; (3) Phenotypic Ratio
1. Cross two homozygous long winged flies.
2. Cross two heterozygous long winged flies.
3. Cross a heterozygous long winged fly with a fly homozygous for long wings.
4. Cross two short winged flies.
5. Cross a short winged fly with a homozygous long winged fly.
6. Cross a short winged fly with a heterozygous fly.
Monohybrid Crosses
(Crosses involving two organisms heterozygous for the same trait)
1. In humans, free earlobes (E) are dominant over attached earlobes (e). A heterozygous
free-earlobed male marries a female with attached earlobes. What will be the possible
phenotypes and genotypes of the offspring?
2. Using the above information, cross two heterozygous free-earlobed parents and give
the genotypes and phenotypes of the offspring.
3. In pea plants, round seeds are dominant to wrinkled seeds. Cross a heterozygous pea
plant with round seeds with a pea plant with wrinkled seeds.
- What are the genotypes of the parents?
- What are the gametes produced by the parents?
- What are the genotypes and phenotypes of the F1 generation?
4. Now, cross two heterozygous round-seeded plants. What will the genotypes and
phenotypes of the offspring be?
5. In Labs, black fur is dominant to yellow. Explain how two black dogs can have
different genotypes. Could a black dog have the same genotype as a yellow dog?