Question

In a plant red colour fruit is dominant over yellow colour. When these two pure lines are crossed, the probability of producing $F_2$ homozygous plants with red fruits, heterozygous plants with red fruits, and plants with yellow colored fruits respectively is

• A. $\frac{1}{4}$ , $\frac{1}{4}$ , and $\frac{2}{3}$
• B. $\frac{1}{4}$, $\frac{1}{2}$ and $\frac{1}{4}$
• C. $\frac{3}{4}$ , $\frac{1}{2}$ and $\frac{1}{4}$
• D. $\frac{1}{4}$, $\frac{3}{4}$ and $\frac{1}{4}$

Answer 1

The correct option is B

$\frac{1}{4}$, $\frac{1}{2}$ and $\frac{1}{4}$

The $F_2$ genotypic ratio of this monohybrid cross is 1:2:1. As the Punnett Square explains, out of the 4 combinations, the probability of homozygous dominant character is $\frac{1}{4}$, that of heterozygous dominant character is $\frac{2}{4}$=$\frac{1}{2}$ , and homozygous recessive character is $\frac{1}{4}$ .