In F2 generation, the crossing of a homozygous tall plant with a homozygous dwarf would yield plants in the ratio of______________
A
Two tall and two dwarf
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B
One homozygous tall, one homozygous dwarf and two heterozygous tall
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C
All homozygous dwarf
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D
All homozygous tall
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Solution
The correct option is B One homozygous tall, one homozygous dwarf and two heterozygous tall
According to the law of dominance, a trait is represented by two contrasting factors of a gene in a heterozygous individual; the allele/factor that can express itself in a heterozygous individual is called as the dominant trait.
The other factor whose effect is masked by the presence of the dominant factor is called recessive factor.
The recessive factor is present in F1 hybrid but is masked by a factor for the dominant trait and that’s why it produced both parental types in F2 progeny.
Owing to a dominance of tallness over dwarfism, a cross between pure breeding tall and dwarf pea plants obtains all heterozygous tall plants in F1 generation.
If dwarfism was dominant characters, it would have expressed itself in F1 generation.
The selfing of heterozygous tall plants yields F2 generation with the genotypic ratio of 1 TT (homozygous tall): 2 Tt (heterozygous tall): 1 tt (homozygous dwarf). Thus, the correct answer is option B.