Question

What fraction of offspring of the cross AaBb × AaBb would be homozygous for both the dominant alleles, assuming that they are on different chromosomes?

A. 1/16B. 1/8C. 1/64D. 1/4E. 1/32

Answer 1

A. 1/16

Step-by-step explanation:

If we break the dihybrid cross of AaBb X AaBb into individual monohybrid crosses:

Aa X Aa :

A a

A AA Aa

a Aa aa

1/4 of the progeny will be homozygous for dominant allele (AA)

Similarly, in cross Bb X Bb 1/4 of the progeny will be homozygous for dominant allele (BB)

Hence, in cross AaBb X AaBb:

1/4 * 1/4 = 1/16 will be homozygous for both the dominant alleles.