== Answer == Yes parents who are both B blood group can have a child with O negative. This is because B blood group only requires one parent gene to be B to have B blood group - they may also have one O gene. People have two blood group genes, one from both parents. B gene is "dominant" as is A gene. O gene is "recessive". AB blood group means a person has one A gene and one B gene B blood group means a person has either one B gene and one O gene or two B genes A blood group means that a person has either one A gene and one O gene or two A genes O blood group means that a person has two O genes Rhesus positive or negative is similar - positive is dominant and therefore a person with one positive gene and one negative will be rhesus positive. A person who is rhesus negative has both negative genes, and received one negative gene from both parents, both who may be rhesus positive ( with one positive and one negative gene each). Importance of O negative blood - O negative blood group is called the "universal donor" because the blood is least likely to cause transfusion reactions so is safest to use in an emergency before blood groups can be identified and matched.
If both parents are A+ can a child be B+?