Can you tell paternity by blood type?

This is a question that is often asked by people inquiring about performing a paternity test. Unfortunately, you cannot determine paternity by using the blood type method alone. Each person inherits ABO Blood Type from their parents. For Example, If a mother is an O blood type and both of the alleged fathers are an A blood type and the child has an A blood type. There is no way to determine the paternity of two or more alleged fathers share the same blood type.

Now, If we use the same example where the child has an A blood type and one of the alleged fathers has a B blood type. We can definitively conclude that the alleged father with type B blood is not the biological father of the child with the A Blood Type. It is important to note, that both A and B Blood Types are dominant types. Therefore one dominant cannot create the other dominant type. Blood Typing can be used to exclude a father but to determine a biological relationship between an alleged father and child.

Can a child have a different blood type than both parents?

Yes. It is possible for a child to have a different blood type than its parents. Here is an example, In the ABO Blood Typing System there are several blood typing outcomes that may occur. AA, AO, BB, BO AB, and OO. For a child to have a different blood type from its parents. One of the parents must carry an AB Blood Type and the other parent must OO. The child’s blood type has two possible outcomes AO or BO. This is the only scenario in which a child will have a different blood type from its parents.

Which parent determines the blood type of the child?

Blood types are determined based on dominant and recessive genotypes. If one parent has A, B, or AB blood type. This parent will be considered dominant. If the other parent is an OO blood type the parent will be deemed recessive. Dominant blood types always win over recessive types. Gender does not play a role in which blood type is dominant or recessive.