Punnett Squares

Question

1. Complete the Punnet Square and calculate % genotype and phenotype for the following 2 crosses:

A) Genotype of parents Tt (M) X tt (F)

1. a. % of each genotype:
2. b. % of each phenotype: % Tall  % dwarf

  B) Genotype of parents Tt (M) X Tt (F)

1. a. % of each genotype:
2. b. % of each phenotype: % Tall  % dwarf

Answer 1

Cross A: Genotype of parents Tt (Male) X tt (Female)

1. Genotypes:
2. Tt: 50% (heterozygous)
3. tt: 50% (homozygous recessive)
4. Phenotypes:
5. Tall (Tt): 50%
6. Dwarf (tt): 50%

Cross B: Genotype of parents Tt (Male) X Tt (Female)

1. Genotypes:
2. TT: 25% (homozygous dominant)
3. Tt: 50%
4. tt: 25%
5. Phenotypes:
6. Tall (TT or Tt): 75%
7. Dwarf (tt): 25%

Explanation: In this PS the offspring have a 25% chance of being homozygous dominant (TT), a 50% chance of being heterozygous (Tt), and a 25% chance of being homozygous recessive (tt). Since T is dominant, both TT and Tt result in the Tall phenotype, which makes up 75% of the outcomes, while tt results in the Dwarf phenotype, making up 25%.

Answer 2

A) Genotype of parents Tt and tt

1. 50% Tt (heterozygous), 50% tt (homozygous recessive)
2. Assuming complete dominance and that a capital T means Tall: 50% Tall and 50% dwarf

B) Genotype of parents Tt and Tt

1. 25% TT (homozygous dominant), 50% Tt (heterozygous), 25% tt (homozygous recessive)
2. Once again, assuming complete dominance and that a capital T is Tall: 75% Tall and 25% dwarf