Question

Three pea plants P, Q and R each having inflated green pods are allowed to grow under natural conditions. 1000 seeds from each plant were collected and there were sown to see the properties of their progenies. The following were the observations:

P	Q	R
1000 have inflated green pods	242 constricted green pods 758 inflated green pods	741 inflated green pod 259 inflated yellow pod

The correct genotypes of these three plants are

• A. $P \, - \, IIGG, \, Q \, - \, IiGg, \, R \, - \, IIGg$
• B. $P \, - \, IIgg, \, Q \, - \, IiGG, \, R \, - \, IiGg$
• C. $P \, - \, IIGG, \, Q \, - \, IiGG, \, R \, - \, IIGg$
• D. $P \, - \, IIgg, \, Q \, - \, Iigg, \, R \, - \, IIGg$

Answer 1

Answer: (C)

Inflated pods are dominant in pea while constricted pods are recessive. Green pods are dominant in pea while yellow pods are recessive. All three plants have inflated green pods. So they should have one of the following genotypes IIGG, IiGG, IIGg or IiGg. These plants were grown naturally it means that there was self pollination.
IIGG x IIGG will produce all plants which are inflated and green. This is seen in plant P.
IiGG x IiGG will produce IIGG, IiGG and iiGG in the ratio $1:2:1$ . Out of these IIGG and IiGG have inflated green pods while iiGG has constricted green pods. Thus Inflated green pods and Constricted green pods are produced in the ratio $3:1$ . This is seen in plant Q
IIGg x IIGg will produce IIGG, IIGg and IIgg in the ratio $1:2:1$ . Out of these IIGG and IIGg have inflated green pods while IIgg has inflated yellow pods. Thus Inflated green pods and inflated yellow pods are produced in the ratio $3:1$ . This is seen in plant R