Question

If a mother has blood group O and father has blood group A, the child being type AB, which of the following is wrong?

(a) The mother may have I^B allele that is passed to daughter

(b) The father of the child is someone else with AB blood type

(c) The child has I^A allele and also I^B allele

(d) This is an abnormal case

This question was posed to me during a job interview.

Query is from Multiple Alleles topic in division Extension and Deviation from Mendelian Genetic Principles of Cytogenetics

Answer 1

Right option is (b) The father of the child is someone else with AB blood type

To explain I would say: Even if the father was someone with AB blood type is not possible for one parent to give both the alleles to their child. This is more likely a case of Bombay blood group where the mother is homozygous for the h antigen and her blood group is not expressed.