Question

In a certain plant, yellow fruit colour $(Y)$ is dominant to green fruit colour $(y)$ and round shape $(R)$ is dominant to oval shape $(r)$. The two genes involved are located on different chromosomes. Which of the following is correct for the condition when plant $YyRr$ is back crossed with the double recessive parent ?

• A. $9 :3 :3 :1$ ratio of phenotypes only
• B. $9 :3 :3 :1$ ratio of genotypes only
• C. $1 :1 :1 :1$ ratio of phenotypes only
• D. $1 :1 :1 :1$ ratio of phenotypes and genotypes

Answer 1

Answer: (D)

$1 :1 :1 :1$ ratio of phenotypes and genotypes

Answer 2

When $YyRr$ is crossed with double recessive parent then genotypic and phenotypic ratio will be $1 : 1 : 1 : 1$. Phenotypic ratio $= 1$ yellow round : $1$ yellow oval : $1$ green round : $1$ green and oval. This represents a test cross.