If a black man marries a white skin female, the mulattoes are born. If such mulattoes intermarry, the progeny will show a gradual gradation of skin colour in the ratio of
Mullatoes have genotype as AaBbCc and if they intermarry, the phenotypic ratio of offspring with skin tone is 1 : 6 : 15 : 20 : 15 : 6 : 1.