Question

Among the offspring of a trihybrid test cross with F${}_1$ hybrid, the ratio of individual heterozygous for all genes to those having other genotypes is

• A. 1 : 8
• B. 1 : 3
• C. 3 : 1
• D. 3 : 2

Answer 1

The correct option is A 1 : 8

A trihybrid cross-examines the segregation of three specific traits in offspring of parents with different gene pairs for each of the three traits.
Here,
Testcross = F${}_1$ hybrid X Recessive parent
= AaBbCc X aabbcc

	ABC	ABc	AbC	Abc	aBC	aBc	abC	abc
abc	AaBbCc	AaBbcc	AabbCc	Aabbcc	aaBbCc	aaBbcc	aabbCc	aabbcc

Heterozygous for all genes = AaBbCc.
Hence, the required ratio = 1 : 8.