Question

In a cross between red kernelled and white kernelled varieties of wheat showing polygenic inheritance the phenotypic ratio in \[{F_2}\] generation will be.
A) \[\;1:{\text{ }}6{\text{ }}:{\text{ }}15{\text{ }}:{\text{ }}20{\text{ }}:{\text{ }}15{\text{ }}:{\text{ }}6{\text{ }}:{\text{ }}1\]
B) \[1{\text{ }}:{\text{ }}4{\text{ }}:{\text{ }}6{\text{ }}:{\text{ }}4{\text{ }}:{\text{ }}1\]
C) \[1{\text{ }}:{\text{ }}2{\text{ }}:{\text{ }}1\]
D) \[2{\text{ }}:{\text{ }}1\]

Answer 1

Hint: In wheat, the colour of the kernel is controlled with the help of two genes, the red colour kernel in wheat is dominant than the white colour. The results are obtained by crossing two pure breeding varieties of wheat i.e. dark red and white.

Complete answer: In wheat, the color of the kernel is estimated with the help of two genes with two alleles i.e. Aa and Bb. The genes A and B represent dominant genes, which indicate the red color and a and b genes represent recessive genes or recessive allele pairs. When red and white color kernels of wheat were crossed, the F₁ generation was observed to be red and even the combination of both red and white pairs. When the cross was done in between \[{F_1}\] generation, the \[{F_2}\] progeny had 5 different types of phenotypic ratio and it was found to be \[1{\text{ }}:{\text{ }}4{\text{ }}:{\text{ }}6{\text{ }}:{\text{ }}4{\text{ }}:{\text{ }}1\].
Parents: AABB (Red) x aabb (White)
Gametes: AB, ab

	AB	Ab	aB	ab
AB	AABB RED	AABb DARK	AaBB DARK	AaBb MEDIUM
Ab	AABb DARK	AAbb MEDIUM	AaBb MEDIUM	Aabb LIGHT
aB	AaBB DARK	AaBb Medium	aaBB MEDIUM	aaBb LIGHT
ab	AaBb MEDIUM	Aabb LIGHT	aaBb LIGHT	aabb WHITE

Hence, the correct answer is option B.

Note: Wheat shows polygenic inheritance that means, several genes combine and affect a single trait. It was demonstrated by H. Nilsson Ehle in wheat kernels.