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Inherited Disorders and Birth Defects




Can 1 type A positive and type AB positive produce a type O negative?


No, this combination cannot produce this blood type, but could possibly produce this Rh factor.

If someone has blood type A, they must have at least one copy of the A form (called an allele) of the ABO gene, but they could have two copies. So a person with blood type A can be either AA or AO.

The same thing is true for blood type B - that person can be either BB or BO.

Someone with blood type AB must have both the A and B alleles. Someone with the blood type O can only have O. In the case you mention, the child must be either blood type A, blood type B or blood type AB - not O.

Blood type = A

Genes = Either AA or AO


Either BB or BO






For the Rh factor, the Rh proteins are arranged into 2 groups - either positive or negative. Each person has two forms (allele) of the Rh gene and the positive form or allele is positive. People with 2 ++ alleles are Rh positive; people with one + and one - allele are Rh positive and people with 2 -- alleles are Rh negative.

Of the different combinations people can have - if both parents are Rh positive, in order to have a child who is Rh negative then - then each parent must have one + and one - allele.

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Response by:

Anne   Matthews, RN, PhD Anne Matthews, RN, PhD
Associate Professor of Genetics
School of Medicine
Case Western Reserve University