Question

In the $F_2$ generation of a monohybrid cross,

• A. all the offspring are heterozygous dominant
• B. all the offspring are homozygous dominant
• C. all the offspring are recessive
• D. recessive, heterozygous dominant and homozygous dominant offspring are obtained in the ratio of 1 : 2 : 1 respectively

Answer 1

The correct option is D recessive, heterozygous dominant and homozygous dominant offspring are obtained in the ratio of 1 : 2 : 1 respectively

A cross between two parents which differ in a single character is called a monohybrid cross.

Two pea plants which are identical in all other characters except one character, say height, if crossed will be an example of monohybrid cross.

The allele for tallness is dominant over that of dwarfness.
'T' allele for tall trait and 't' allele for dwarf trait.

When a tall plant is crossed with a dwarf plant, all the $F_1$ hybrids are tall (heterozygous dominant).

When these $F_1$ hybrids undergo selfing, $F_2$ generation is produced.

In $F_2$ generation recessive (tt), heterozygous dominant (Tt) and homozygous dominant (TT) offspring are obtained in the ratio of 1 : 2 : 1 respectively.


The genotypic ratio of $F_2$ generation is 1 : 2 : 1.

Out of 4 plants in $F_2$ generation, 1 is homozygous dominant (TT), 2 are heterozygous dominant (Tt) and 1 is recessive (tt).

Hence option d is correct.