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 ration of the offspring of a bbpp x bbpp cross if these alleles sort independently?

A dominant trait can be described as the one which masks the effect of a recessive trait. The alleles for a recessive trait gets suppressed by the dominant one.

A punnet square can be described as a diagram which depicts the outcomes of a cross. For single traits, the cross is monohybrid. For studying two traits at a time, a dihybrid cross can be made.

The punnet square for the following Holstein cattle can be shown as:

           BP           Bp          bP             bp

BP     BBPP     BBPp     BbPP         BbPp

Bp     BBPp     BBpp     BbPp          Bbpp

bP      BbPP     BbPp     bbPP          bbPp

bp      BbPp      Bbpp     bbPp          bbpp

The results show the phenotypic ratio to be 9 black/polled : 3 black/horned : 3 red/polled : 1 red/horned