Question

In holstein cattle, the allele for black hair color (b) is dominant over the allele for red hair color (b), and the allele for polled (p), or lacking horns, is dominant over the allele for having horns(p). what is the expected phenotypic ratio of the offspring of a bbpp × bbpp cross if these alleles sort independently?††

Answer 1

I hope you meant, a cross between BbPp and BbPp, else for bbpp x bbpp, all the progeny will be bbpp.

We need to work out a Punnett square to determine the genotypes resulting from the cross between BbPp and BbPp. The dyhybrid cross results in 16 different genotypes, of which a few have the same phenotypes.

It can be seen that there are 4 different kinds of phenotypes present, in the ratio 9:3:3:1.