UPDATE: CAN A BLOOD TYPE AB/O COUPLE HAVE AB AND O CHILDREN? According to the blood type calculator, an AB and O couple can only have children who are either A or B. The genotypes for both would be AB and OO, so with the O being recessive, only either the A or B can be passed on from the AB partner and the O would not show up in the phenotype. So how come several AB and O couples have found me to alert me that they have children who are both phenotype AB and O? The allele which they carry is called cisAB where both, the A and the B is being encoded into one allele and in … Continue reading What is cisAB?