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Inherited Disorders and Birth Defects

Blood type



I have B positive blood type and my wife has O positive blood type. Will my daughter have my blood type or my wifes blood type?


Your daughter could have either blood type.

For the A and B blood type groups, there are 2 forms (alleles) of the gene (genotype) that codes for the blood type. The different forms are: AA, AO or BB, BO or AB. The other blood type is OO.

AA and AO look exactly the same on a blood typing test as does BB and BO. In your case, you may have BB as your genotype or BO as your genotype - on the blood test they look the same. For your wife, since she has O blood type, she only has the genotype, OO.

When we pass on our genes to our children, each parent gives 1 form (allele) for each gene so the child gets 1 allele from her dad and 1 allele from her mom. When you pass on the genes for your blood type to your children, if you have the BB genotype, you can only pass on a B. If you have the BO genotype, you can pass on either the B or the O. Your wife can only pass on an O. If your daughter inherits the B from you and the O from her mother, she will have type B blood type. If you happen to have the BO form - you could pass on an O to her and then she would have gotten an O from you and an O from her mother and have O blood type.

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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