Question: 140: What is the expected percentage of F_{2} progeny with yellow and inflated pod in dihybrid cross experiment involving pea plants with green coloured, inflated pod and yellow coloured constricted pod?
(1) 100 \%
(2) 56.25 \%
(3) 18.75 \%
(4) 9 \%
Answer: Option (3)
Explanation:
In pea plants, green pod colour is dominant over yellow pod colour, and inflated pod shape is dominant over constricted pod shape.
Let green pod colour be represented by G and yellow by g,
while inflated pod shape is represented by I and constricted by i.
The parental cross is between green, inflated pod (GGII) and yellow,
constricted pod (ggii).
All F_{1} progeny will be heterozygous (GgIi) and show green, inflated pods.
On selfing the F_{1} plants, a dihybrid cross is obtained with the phenotypic ratio 9:3:3:1.
The phenotype yellow and inflated corresponds to the genotype ggI\_,
which appears in 3 out of 16 offspring.
The percentage of such progeny is \frac{3}{16} \times 100 = 18.75 \%.
Therefore, the expected percentage of F_{2} progeny with yellow and inflated pods is 18.75 \%.