Question

A couple, both of whom have blood type B, are recruited for a study on the genetics blood types. Their first child is blood type 0 (null), causing the scientists conducting the study to accuse the mother of infidelity and throw them out of the study. Which of the following statements is true? A) The scientists in this study have correctly accused the mother. B) A grandparent likely was heterozygous for blood type 0 (null). C) The mutated gene was x-linked and the first child was male. D) The first child is heterozygous for blood type 0 (null) E) None of the above are correct

Answer 1

there are six possible combinations of genes, namely OO, OA, OB, AA, BB, AB; and combination of these genes are called as Genotypes such that each person has any one of these. This genetic determination of the progeny depends on the genotype of the parents (both mother and father). therefore any set of parents could be of three genotype - AO, BO, OO

in the given case, both parents said to be having same group type B with their 1st child as group type O.

if the child was having a B type blood group then it was to be called as pure-breed offspring for the B-gene. but here the child is having O blood group. so yes, this is possible even if both parent has blood group B and the child is blood group O. Therfore, two parent with B blood group can produce a child with B or O blood type.

ABO bloodtypes are difficult to understand because the 'O-type' antigen is masked by the presence of an A or B type antigen.

So with genotype AO or AA - blood group is A

" " BO or BB - blood group is B

" " AB - blood group is AB

" " OO - blood type is O

so possibly both parents could have contributed their recessive O gene to their child and when this happens the child expresses O blood type instead of B blood type.

(based on this my answer is option B)