Question

In a monohybrid cross the ratio of F2 true breeding dominant and true breeding recessive would be
A) 50:50
B) 25:25
C) 75:25
D) 25:75

Answer 1

Hint: In case of Mendel’s monohybrid cross, one tall dominant (TT) plant and One short recessive (tt) plant were crossed together and it results in the formation of homozygous and heterozygous plants as well.

Complete answer:
Let’s discuss the options and find the correct answer.
In case of the mating, two taken plants are homozygous in nature between which one is homozygous dominant and other is homozygous recessive. At their first mating, in the $F_1$ generation, the offspring produced are all become heterozygous dominant (Tt). The punnett square is given below.

alleles	T	T
t	Tt	Tt
t	Tt	Tt

After that, when the plants produced in F1 generation that are heterozygous in nature are crossed together. As a result of crossing between two heterozygous plants (Tt), In $F_2$ generation, four offspring will produce and they are homo- and -heterozygous in nature. As a result of the rating, three dominant tall plants and one recessive short plant will produce. So, their phenotypic ratio will be 3:1. But they all are not genetically the same i.e. there is a difference in their genotypic ratio. Punnett square is given below

alleles	T	t
T	TT	Tt
t	Tt	tt

So, one true breeding dominant plant (TT), two heterozygous dominant plants (Tt) and one true breeding recessive plant (tt) will be produced in $F_2$ generation.

Hence option ‘B’ is the correct answer.

Note:In $F_2$ generation, 25% tall plant, 25% short plant, and 50% heterozygous dominant plant will be produced and the phenotypic percentage ratio will be 75:25.