GENETICS PROBLEMS
Name:_______________________Period:____
For all genetics problems:
1) Make a key Dominant trait - capital letter & Recessive trait – lowercase letter (1 point)
2) Write out parents' genotypes (1/2 point)
3) Write out all possible gametes (1/2 point)
4) Do Punnett square (1 point)
5) Write possible genotype ratios (numbers and letters: ex. 2AA:2Aa) (1/2 point)
phenotype ratios (numbers and appearance: ex. 2 Round: 2 wrinkled) (1/2 point)
Use the following information to answer questions 1 and 2 (the same key may be used for both):
Green seeds are dominant to yellow seeds
Q#1. Cross a homozygous yellow parent with a homozygous green parent.
1.Key
=
=
=
3.Gametes
2. Parent Genotypes
X
X
4. Punnett Square
5.Genotype ratios:
Phenotype ratios:
Q#2. Cross a heterozygous green parent with a heterozygous green parent.
1.same Key
2. Parent Genotypes
X
3.Gametes
X
4. Punnett Square
5.Genotype ratios:
Phenotype ratios:
Use the following information to answer Questions 3 - 5 (again, the same key may be used for all
3 problems)
Purple is dominant to white flowers and tall is dominant to short plants.
Q#3. A heterozygous purple, short plant is crossed with a white, homozygous tall plant.
1.Key (used for #3,4,5)
2. Parent Genotypes
=
=
=
X
3. Possible Gametes
X
=
=
=
4. Punnett Square
5.Genotype ratios:
Phenotype ratios:
Q#4. A homozygous purple, heterozygous tall plant is crossed with a white short plant.
2.Parent Genotypes
X
3.Possible Gametes
X
4. Punnett Square
5.Genotype ratios:
Phenotype ratios:
Q#5. A heterozygous purple, heterozygous tall plant is crossed with a white short plant.
1. Parent Genotypes
3.Punnett Square
X
2. Possible Gametes
X
5.Genotype ratios:
Phenotype ratios:
Q#6. A pea plant that breeds true for round, yellow seeds (RRGG) is crossed with a plant that
breeds true for wrinkled, green seeds (rrgg). Do the 5 steps for this problem.
1.Key
2. Parent Genotypes
=
=
=
X
3. Possible Gametes
X
=
=
=
4.Punnett Square
5. Genotype ratios:
Phenotype ratios:
Q#7. The F1 seeds from Problem #6 are planted and their flowers are allowed to self-pollinate.
Do the 4 steps for this problem (you don't have to do the key again), except only do phenotype
ratio for step #5.
2. Parent Genotypes
X
3. Possible Gametes
X
4. Punnett Square
5.Phenotype ratios only:
Again referencing the traits from problem #7, two round yellow parents were crossed. Many
offspring were produced by many crossings. The results were:
Round Yellow
132
Round Green
41
Wrinkled Yellow
49
Wrinkled Green
15
What is the phenotypic ration of these offsprings (actual and rounded)? Must show your work for
the math.
What was the most likely genotype of the parents?
Q#8 A&B. A cross between the black (BB) and white (WW) varieties produces the so-called
"blue" (really gray) (BW) Andalusian variety of chicken. Only a single gene is involved.
**What type of dominance is this? (Complete, Incomplete, or Co-dominance).
Do the 5 steps for the following crosses (only one key is necessary for all):
A. A blue crossed with a blue
1.Key
2. Parent Genotypes
=
=
=
X
3.Gametes
X
4. Punnett Square
5.Genotype ratios:
Phenotype ratios:
B. A blue crossed with a white
1.Key
=
=
=
3.Gametes
2. Parent Genotypes
X
X
4. Punnett Square
5.Genotype ratios:
Phenotype ratios:
Circle one.
Q#9. Use the following information for the sex-linked cross below. Normal blood is dominant to
hemophiliac blood. Hemophilia is linked to the X chromosome. Do all steps for question A. again,
only needing one key for all three parts.
A. Cross a carrier female with a hemophiliac male.
Key:
2. Parent Genotypes
=
X
=
3. Possible Gametes
X
=
=
4.Punnett Square
=
5. Genotype ratios:
Phenotype ratios:
B. Of the children, how many could be hemophiliacs?
C. Of the boys, how many could be normal blood?
Q#10. Color-blindness is an X-linked recessive trait. Two parents with normal vision have four
children, 2 boys and 2 girls. Both girls have normal vision. One boy is normal, but one boy is
colorblind. What did the genotypes of the parents have to be to have these children? Do all 5
steps to answer the question.
1.Key
2.Parent Genotypes
=
X
=
3. Gametes
X
4.Punnett Square
=
=
=
5. Genotype ratios:
Phenotype ratios:
Q#11. The colorblind boy in Q#10 grows up and marries a woman with normal vision. They
have 6 children (wow!): 2 girls and 4 boys. All have normal vision. What was the most likely
genotype of the woman. (which “normal” was she?) Do the crosses to show your answer. Use
the key from Q#10
2 possible phenotype for mom: _______________ Or _________________
2.Parent Genotypes
X
3. Gametes
X
4.Punnett Square