If B represents the allele for black hair and b represents the allele for white hair then a cross between Bb and Bb will lead to the following kind of progenies.
Parental: Bb x Bb
F1 : BB Bb Bb bb
Genotypic ratio : 1:2:1
Phenotypic ratio : 3:1
The phenotypic ratio indicates that three of the four off springs will have black hair while one of the four off springs will have white hair.
Amongst 3 offsprings which have black hair, one will be homozygous dominant whereas other two which have black hair color will be heterozygous dominant.
