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
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C
3:1 :: Tall : Dwarf
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D
3:1 :: Dwarf : Tall
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Solution
The correct option is A 1:2:1 :: Tall homozygous : Tall heterozygous : Dwarf A cross between pure breeding tall (TT) and dwarf (tt) plants produce all tall (Tt) plants in F1 progeny. These heterozygous tall plants produce 50% gametes with "T" allele and 50% with "t" allele. Random fusion of these gametes from two heterozygous tall plants gives tall and dwarf plants in 3:1 ratio. out of 3/4 tall plants; 1/4 are homozygous tall (TT) and 2/4 are heterozygous tall (Tt). This makes the genotypic ratio for F2 generation as 1 homozygous tall (TT): 2 heterozygous tall (Tt): 1 homozygous dwarf (tt). This makes option B incorrect and option A correct. Option D is incorrect as 3/4 plants are tall while 1/4 are the dwarf in F2 generation. Option C is incorrect as the question is asking the genotypic ratio. The correct answer is A.