If I am blood type B, what are all the possible genotypes that could be expressed by my parents?

I think it might be 16 but I was reading online and saw this:

Similarly, someone who is blood type B could have a genotype of either BB or BO.

So if someone can help me answer this, that would be great.


Parent 1 and 2 have each 5 possible genotypes (OO, AO, BB, BO and AB).

Here a Punnett square with each possibilities. I highlighted the possible parent genotypes.

enter image description here

The total number of possible crosses is exactly 21. Note that here A = Ia, B = Ib and O = i.


This is starting from the information based on your blood type only (i.e. no information about your genotype).

Some background information. Antigen expressing alleles (here referred as Ia or A and Ib or B) are dominant. Not expressing an allele is notated i or O. Being of blood type O is when you don't express both alleles so it is a recessive trait (only possible genotype is ii or OO genotype).

  • 2
    $\begingroup$ You probably shouldn't call an AB individual homozygous. $\endgroup$
    – canadianer
    Mar 25 '15 at 18:41
  • 1
    $\begingroup$ @canadianer thanks for pointing that out. Modified the table. $\endgroup$ Mar 25 '15 at 18:48
  • 3
    $\begingroup$ Your answer is better, so I'll just delete mine to avoid confusion. $\endgroup$ Mar 25 '15 at 18:58
  • 1
    $\begingroup$ @poka.nandor was getting messy without a table ;) $\endgroup$ Mar 25 '15 at 18:59
  • 2
    $\begingroup$ @cagliari2005 yeah I should have done the same to avoid missing possible crossings. I feel bad about it... I mean not about you having a better answer, but about me being careless. $\endgroup$ Mar 25 '15 at 19:01

21 crosses could be many more if you considered minor types as A2, A3, B3 or hybrid alleles as Ax, Bx or chimera AB alleles as cis-AB, B(A). These rare phenotypes break standard 4 type rules, for example, Ax/O genotype could be both type A or type O. It depends if you talk about genetcis or blood compatibility.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.