Question

Pure-tall (TT) pea plants are crossed with pure-dwarf (tt) pea plants. The pea plants obtained in F1 generation are then self-pollinated to produce F2 generation. 
(i) What do the plants of F1 generation look like? Justify your answer. 
(ii) What is the ratio of pure-tall plants to pure-dwarf plants in F2 generation?

Hint:

In the F2 generation, a 3:1 phenotypic ratio is observed when crossing two heterozygous plants (Tt).

Answer 1

(i) The plants in the F1 generation will all be heterozygous (Tt), as tall (T) is dominant over dwarf (t). Hence, all F1 generation plants will exhibit the tall phenotype. 
(ii) In the F2 generation, the F1 plants (Tt) are self-pollinated. The resulting offspring will follow a 3:1 phenotypic ratio, with three tall plants for every one dwarf plant: \[ {Phenotypic ratio:} \ 3 \ {tall}: 1 \ {dwarf} \] 
Thus, the ratio of pure-tall plants (TT) to pure-dwarf plants (tt) in F2 generation is 1:3.