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Question:

A tall true breeding garden pea plant is crossed with a dwarf true breeding garden pea plant. When the F1 plants were selfed the resulting genotypes were in the ratio of 1:2:1 :: Tall homozygous : Tall heterozygous : Dwarf

1:2:1 :: Tall heterozygous : Tall homozygous : Dwarf

3:1 :: Tall : Dwarf

3:1 :: Dwarf : Tall

1:2:1 :: Tall homozygous : Tall heterozygous : Dwarf

Solution:

A cross between pure breeding tall (TT) and dwarf (tt) plants produce all tall (Tt) plants in F1 progeny. These heterozygous tall plants produce gametes T and t in equal proportion. Selfing of F1 plants (Tt x Tt) will produce offspring with genotypes TT, Tt, and tt in a 1:2:1 ratio. This corresponds to a phenotypic ratio of 3 tall (TT + 2Tt) : 1 dwarf (tt).