Question

A tall true breeding garden pea plants is crossed with a dwarf true breeding garden pea plant. When the F1 plants were selfed the resulting genotypes were in the ratio of

• A. 3 : 1 :: Tall : Dwarf
• B. 1 : 2: 1 :: Tall homozygous : Tall heterozygous : Dwarf
• C. 1 : 2: 1 :: Tall homozygous : Dwarf : Tall heterozygous
• D. 3 : 1 :: Dwarf : Tall

Answer 1

The correct option is B 1 : 2: 1 :: Tall homozygous : Tall heterozygous : Dwarf

When a tall true garden pea plant is crossed with a true dwarf plant. All the offspring obtained in the F1 generation were tall (Tt).
When the F1 plants were selfed the resulting genotypes were in the ratio of 1 : 2: 1 :: Tall homozygous : Tall heterozygous : Dwarf.
This can be explained by the following cross.

Parents TT x tt

	T	T
t	Tt (Tall)	Tt (Tall)
t	Tt (Tall)	Tt (Tall)

F1 generation - All Tt (Tall plants)
On selfing plants of the F1 generation we get,
Tt x Tt

	T	t
T	TT	Tt
t	Tt	tt

F2 generation : TT, Tt, Tt, tt (Tall and Dwarf plants in the ratio of 3:1)
Therefore,
Phenotypic ratio : 3 : 1
Tall : Dwarf
Genotypic Ratio : 1 : 2 : 1
TT (Homozygous) : Tt (Heterozygous) : tt (Homozygous)

Therefore, option b) 1 : 2: 1 :: Tall homozygous : Tall heterozygous : Dwarf is the correct option.