If a man and a woman , both habing blood type B, have 12 children , 3/4 are of type B and 1/4 are of O , what are the genotypes of the parents?
1 Answer
Dec 3, 2015
Genotype of both parents is Bo.
Explanation:
The parents can be either BB or Bo genotypically, so we use these options to exploit all possible combinations using test-cross Punnett squares.
BB x Bo will give half BB and half Bo genotypes, meaning the offspring will be 100% of blood type B. However, this is not the correct combination for the sought progeny.
Another combination is Bo x Bo which will give a quarter BB, two quarters (one half) Bo, and a quarter oo. Therefore, phenotypically the genes will be expressed in the offspring as three quarters of blood type B and one quarter of blood type O.
