Blood Types Problem Set

Problem 4: What are the potential blood types of the father of my son?


I have been reading your info about inheritance of blood types and I am getting very confused! I am trying to figure out what blood type the father of my son could have since my son and I are both type A+. Also, my brother is type 0 and my mom is A+. We can't find anything that explains how this can be. Could you please help??? --From a concerned Mom

The father could be:
A. A, AB, B, or O Dr. Hallick's reply:

Unfortunately for this particular case, one cannot distinguish between any potential fathers from blood type alone. Note from the table that a mother with type A blood could have created a child with type A blood with a father of any of the four possible blood types, type A, type AB, type B, or type O. Likewise, the father of the child could be either Rh+ or Rh-.

It should be apparent from this discussion that blood type is not a very good test for paternity. In some cases, unambiguous information can be obtained, i.e. a type AB male cannot father a type O child. However in most cases, the results are uncertain.

If determining the paternity of a child is important, there are very sensitive DNA test currently available that can establish paternity to a certainty in excess of 99.99%, or exclude someone as the biological father with absolute certainty. Elsewhere in the Biology Project is an exercise to follow the inheritance of DNA markers in a paternity study.

B. Either A or B
C. Either A or O

The Biology Project
Department of Biochemistry and Molecular Biophysics
University of Arizona
Thursday, October 23, 1997
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