My Blood Type Is O+?

My blood type is O+. My parents are B+ and AB+. I read that combinations that can occur for parents BB or BO (Type B) and AB (Type AB) are only B, A or AB children. How did I get O+ blood type?

No it’s not possible. First, let me explain the ABO blood groups. A = AA or AO B = BB or BO AB = AB O = OO You need to get an O allele from both parents to have blood type O. The AB parent has no blood allele to give, so his child can’t be blood type O. But there’s a few ways a parent with blood type AB can have a child with blood type O. If that parent is cis-AB (that is carrying A and B alleles on the same chromosome) and the other allele is O, the parent will have the alleles (AB)O and may pass the O allele to his/her child. If the child also receives an O allele from the other parent, he/she will have blood type O. Another way is if the child has Bombay Phenotype (hh). This child will not produce any antigens so he will be genetically tested as O even though he’s actually A, B or AB. While it’s very rare for a parent with blood type AB to have a child with blood type O, it’s still possible.