Inheritance of Blood Types

This article presents information on the different blood types, and also the inheritance of blood types. Human blood contains the same basic elements like RBC, WBC and platelets, but still, all blood is not alike. Read on to know what makes your blood different from your mother’s blood.

Our body-parts receive oxygen and other nutrients through the blood. Healthy blood plays an important role in strengthening our immune system and enhancing the functions of all bodily organs. But when it comes to scarcity and transfusion of blood, you cannot accept any blood. The blood group or blood type of the donor needs to match the blood group of the receiver. Blood types are determined according to the presence or absence of certain antigens. There exist 8 common blood types.

Common Blood Types

The main components of blood are plasma (the liquid component of blood), red blood cells (RBCs), and white blood cells (WBCs). Blood groups of both the parents determine the blood group of a child. The inherited antigenic substances (antibody generators or simply antigens) are present on the surface of the red blood cells (RBCs). Apart from A and B antigens, another antigen called Rh factor is also taken into consideration while determining the blood group of an individual. Different systems are used to classify blood, but here, we are going to take a look at the ABO blood group system with Rh factor (Rhesus factor). The presence or absence of A-antigens and B-antigens, and presence or absence of the Rhesus-D antigen, determine the blood type. Here is a list of the main blood groups.

• Blood Group ‘A’: Red blood cells have the ‘A antigen’ and the plasma contains anti-B antibodies.
• Blood Group ‘B’: Red blood cells have the ‘B antigen’ and the plasma contains anti-A antibodies.
• Blood Group ‘AB’: Red blood cells have both, A and B-antigen, and the plasma contains neither anti-A nor anti-B antibodies.
• Blood Group ‘O’: Red blood cells have neither A nor B antigen, and the plasma contains both anti-A and anti-B antibodies.

Depending upon the presence or absence of the Rh factor, the eight blood types are: A Rh+, A Rh-, B Rh+, B Rh-, AB Rh+, AB Rh-, O Rh+ and O Rh-.

Inheritance Patterns of Blood Groups

The anti-A and anti-B antibodies are developed during the first years of life, as a response to the food, bacteria and viruses entering the body. Placental sensitization is responsible for the development of the Rh-D antibody in the blood of the baby. The blood type of the baby is determined by the blood type of both the father and the mother. The following blood types chart will help you better understand the possible blood type of a child.

The above chart shows that parents with O blood type can produce a child with only O blood type. If both parents have A blood type, then they can produce a child with either A or O blood types. When both parents have B blood type, their child can have either B or O blood type. A child can have A, B, AB or O blood type, when one of the parents has A blood type and another has B blood type, or when both parents have AB blood type. Similarly, when one parent has A and another has AB blood type, their child can be born with A, B or AB blood types. One parent with B blood type and another with O blood type can produce a child with B or O blood types. Moreover, both parents with Rh+ blood types can have a child with Rh- blood type. For Rh factor inheritance, you may refer to the following chart.

There are exceptions to the above rules of inheritance of blood types and they are referred to as ‘Bombay phenotypes’, since they were first discovered in Bombay. Consanguineous mating in which parents are blood relatives (e.g., first cousins) often give birth to Bombays. If they require blood, they need to get it from another Bombay. Most often, blood obtained from the blood relatives (especially siblings) matches the blood of Bombays.