Question

Short / Long answer type questions.
A dihybrid heterozygous round yellow seeded garden pea (Pisum sativum) offspring was crossed with a double recessive parent. (a) What type of a cross is this? b) Work out the genotype and phenotype of the progeny. (c)What principle of Mendel is illustrated through the result of this cross?

Answer 1

	RY	Ry	rY	ry
ry	RrYy (round yellow)	Rryy (round green)	rrYy (wrinkled yellow)	rryy (wrinkled green)

Heterozygous pea: RrYy

Double recessive parent: rryy

(a) This is dihybrid cross as there are two characters being studied simultaneously.

(b) Genotype: All four combinations appear once i.e. RrYy, Rryy, rrYy, and rryy. (1: 1: 1: 1)

Phenotypes: Round yellow, round green, wrinkled yellow, wrinkled green. (1: 1: 1: 1).

(c) This cross illustrates the law of independent assortment which states that the inheritance pattern of one kind of character is independent of the inheritance pattern of the other character. Here, inheritance of seed shape (round or wrinkled) is independent of the inheritance of seed colour (yellow or green).