Health News

On blood types and gene pools

Q: My husband has a blood type of AB, my blood type is O. Will our baby have be an O, A or B blood type?

A: When your baby was conceived you and your husband contributed equally to your baby's gene pool. You both passed on to your baby dominant and recessive genes. It is the unique combination of that special gene pool that will determine how your baby looks and what blood type he or she will have.

Blood type is determined by the dominant alleles you both passed to your baby. Alleles are a pair of genes that are on chromosomes. Genes are the basic unit of heredity. We receive 23 chromosomes from each of our parents. That is why your baby could have your nose and your husband's ears.

There are dominant and recessive genes. Dominant genes will prevail over the recessive genes and produce a characteristic trait. In the case of blood types, the dominant alleles from each parent will determine the baby's blood type. There are many possible combinations.

There are three different alleles for human blood types. There are A, B and O. Most recognized blood types of humans are: A, B, AB and O. Since there are 4 different blood types and both the mother and the father are contributing to the determination of the baby's blood type, there are 16 different possible combinations. That is because we have to take into account both the dominant and the recessive factors in the blood type. Since you are type O, you will pass on the O allele. Your husband however can pass on either the A or the B allele. Your baby could have A or B blood type. That is because O does not have antigens.

Our blood has many properties. Blood types are commonly determined by the presence and or absence of certain antibodies and certain antigens. Antigens stimulate the body to make antibodies. Antibodies are protein substances that are produced in the body to fight organisms that it recognizes as harmful to the body.

Type A blood has an anti B antibody and an A antigen. Type B blood has an anti A antibody and a B antigen. Type AB blood has no antibodies and A and B antigens. Type O blood has anti A and anti B antibodies but has no antigens. The Coombs Test, named after the doctor that invented it, is done when there may be a blood discrepancy between a mother and a baby's blood. If the mother's blood type is O and the baby is A, B or AB then the test would be done. If the Mother's blood type is A, B or AB and the baby is O then it would not be done. Remember, the A,B and AB, blood types have antigens but the O blood does not. If the baby has O type the mother would not form A and B antibodies against the baby.

When I was a little girl my father used to always say, blood is thicker than water. I never really understood what it meant. Now I have a better understanding. Our blood is a result of our ancestors passing on genes therefore we are always going to defend our family first and foremost.

Katie Powers, R.N., is a board-certified lactation consultant and perinatal educator at Manatee Memorial Hospital's Family BirthPlace. Her column appears every other week in Healthy Living. Contact her at