Question

The genotype of green stemmed tomato plant is denoted by ‘GG’ and that of purple stemmed tomato plant as ‘gg’. Hybrid of a cross between these two were self-pollinated to obtain F₂ progeny. What will be the ratio of GG, Gg and gg in this F₂ progeny?

Options

• 2 : 1 : 1

• 3 : 1 : 0

• 1 : 1 : 2

• 1 : 2 : 1

Answer 1

1 : 2 : 1

Explanation:

The parents are homozygous, containing green-stemmed (GG) and purple-stemmed (gg) plants. Each parent produces one type of gamete (G or g). The resulting F₁ hybrid is entirely heterozygous (Gg). Crossing the F1 hybrids produces the F₂ progeny. 

Using a Punnett square, we can determine the possible combinations of alleles:

	G	g
G	GG	Gg
g	Gg	gg

By counting the genotypes from the Punnett square, we find that GG : 1, Gg : 2 and gg : 1. This results in a ratio of 1 : 2 : 1.