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

A. 1/16

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.

layer 3 is younger than layer 6.