What are the expected phenotypic ratios from the following cross:
Tt Rr YY Aa × Tt rr Yy Aa,
where T = tall, t = dwarf, R = round, r = wrinkled, Y = yellow, y = green, A = axial, a = terminal; T, R, Y, and A are dominant alleles. (Note: multiplication method or forked-line method)
The expected phenotypic ratios can be calculated using the multiplication method:
1. Write out the genotypes of the parents:
Tt Rr YY Aa × Tt rr Yy Aa
2. Determine the possible gametes for each parent:
TtRrYYAa: TRYA, TRYa, TRyA, TRya, TyYA, TyYa, Ty yA, Ty ya, tRYA, tRYa, tRyA, tRya, tyYA, tyYa, ty yA, ty ya
TtrrYyAa: trYA, trYa, tryA, trya, tYYA, tYYa, tYyA, tYya, trY A, try a, tYY A, tYYa, tYyA, tYya, tryA, trya
3. Use the Punnett square to determine the possible offspring genotypes:
T t R r Y Y A a
T t R R Y Y A a TRYA TRYa TRyA TRya TyYA TyYa Ty yA Ty ya
T t r r Y y A a trYA trYa tryA trya tYYA tYYa tYyA tYya
4. Count the number of each genotype:
- TRYA: 1
- TRYa: 1
- TRyA: 1
- TRya: 1
- TyYA: 1
- TyYa: 1
- Ty yA: 1
- Ty ya: 1
- trYA: 1
- trYa: 1
- tryA: 1
- trya: 1
- tYYA: 1
- tYYa: 1
- tYyA: 1
- tYya: 1
5. Determine the phenotypes for each genotype:
- Tall, round, yellow, axial: 4/16 or 25%
- Tall, round, yellow, terminal: 4/16 or 25%
- Tall, round, green, axial: 1/16 or 6.25%
- Tall, round, green, terminal: 1/16 or 6.25%
- Tall, wrinkled, yellow, axial: 1/16 or 6.25%
- Tall, wrinkled, yellow, terminal: 1/16 or 6.25%
- Tall, wrinkled, green, axial: 1/16 or 6.25%
- Tall, wrinkled, green, terminal: 1/16 or 6.25%
- Dwarf, round, yellow, axial: 1/16 or 6.25%
- Dwarf, round, yellow, terminal: 1/16 or 6.25%
- Dwarf, round, green, axial: 1/16 or 6.25%
- Dwarf, round, green, terminal: 1/16 or 6.25%
- Dwarf, wrinkled, yellow, axial: 0/16 or 0%
- Dwarf, wrinkled, yellow, terminal: 0/16 or 0%
- Dwarf, wrinkled, green, axial: 0/16 or 0%
- Dwarf, wrinkled, green, terminal: 0/16 or 0%
Therefore, the expected phenotypic ratios are:
- 25% tall, round, yellow, axial
- 25% tall, round, yellow, terminal
- 6.25% tall, round, green, axial
- 6.25% tall, round, green, terminal
- 6.25% tall, wrinkled, yellow, axial
- 6.25% tall, wrinkled, yellow, terminal
- 6.25% tall, wrinkled, green, axial
- 6.25% tall, wrinkled, green, terminal
- 6.25% dwarf, round, yellow, axial
- 6.25% dwarf, round, yellow, terminal
- 6.25% dwarf, round, green, axial
- 6.25% dwarf, round, green, terminal