Question

What are the genotypes of the parents in the example?
A
TTRr and ttRr
B
TtRr and TtRr
C
TTrr and TtRr
D
TTRr and TtRr

Answer 1

I don't have the example you mean. Could you paste the offspring phenotypes or the ratios/numbers from the example?

Meanwhile, here is a quick guide you can use to pick the correct option:

- B (TtRr × TtRr) → classic dihybrid cross gives a 9:3:3:1 phenotypic ratio (independent assortment of two heterozygotes).

- A (TTRr × ttRr) and D (TTRr × TtRr) → both give all offspring tall (because at least one T is always contributed) and a 3:1 ratio for the R phenotype (dominant vs recessive). They differ in the proportion of TT vs Tt among offspring:
- A produces 100% Tt (no TT) because one parent is TT and the other is tt.
- D produces a mix of TT and Tt (about 1:1 in the example calculation).

- C (TTrr × TtRr) → all offspring are tall (T present) and R vs r shows a 1:1 phenotypic ratio (half R_ and half rr).

If you tell me the observed offspring phenotypes or numbers (e.g., “all tall, 3/4 R_ and 1/4 rr” or “9:3:3:1”), I’ll pick the correct letter and show the Punnett reasoning.