Question

In two independent crosses between tall pea plants and dwarf pea plants, the following observations were noted down:

In the first cross, the offspring population had an equal number of tall and dwarf plants.

In the second cross, the offspring population had only tall plants.

Work out the crosses, and explain the difference in the offspring populations.

Answer 1

In the first cross, the genotype of parents would be Tt and tt.

Gametes	T	t
t	Tt	tt
t	Tt	tt

The ratio of progeny is 1:1.

The offspring population will have an equal number of tall plants (Tt) and dwarf plants (tt).

In the second cross, the genotypes of the parents would be TT and tt

Gametes	T	T
t	Tt	Tt
t	Tt	Tt

Progeny: All will be Tt

The offspring population will only have tall plants.
The difference is due to the different genotypes of the parents.