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Name: Laurie
Status: Educator
Grade:  4-5
Location: WA
Country: United States
Date: Winter 2009 - 2010

If O type blood is the oldest, why is it recessive?

The gene for type A and B antigens code for antigens which appear on the red blood cell. The gene for type O antigen does not code for an antigen. If you carry one of each, type O and type A for example, then your red blood cells will carry the type A antigen.

Ron Baker, Ph.D.


One of the biggest misconceptions in genetics is the incorrect idea that recessive genes are weak. The word recessive gives that idea, but in reality, and in this case, the Type O gene really means that there is no protein being produced. Type O means zero or nothing in a sense. Type A and B are labels given to types of blood group proteins. If you have the alleles O and A (one from each parent), you will have type A blood because the A protein is present and the O (no protein) means A is seen. Hence, in this case, the label of "recessive". Type O is called recessive only because nothing is there.

Steve Sample

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