Blood Inheritance
ABO Blood Type
Everyone has an ABO blood type (A, B, AB, or O) and an Rh factor (positive or negative). Just like eye or hair color, our blood type is inherited from our parents.
Each biological parent donates one of two ABO genes to their child. The A and B genes are dominant and the O gene is recessive. For example, if an O gene is paired with an A gene, the blood type will be A.
For instance, a parent with O blood with 2 O genes and a parent with A blood with 2 A genes will have an A blood type child with one A gene and one O gene.
Parent Genes |
AA |
BB |
AB |
OO |
AO |
BO |
AA |
AA |
AB |
AA, AB |
AO |
AA, AO |
AB, AO |
BB |
AB |
BB |
AB, BB |
BO |
AB, BO |
BB, BO |
AB |
AA, AB |
AB, BB |
AA, BB, AB |
AO, BO |
AA, AO, BO, AB |
BB, BO, AB, AO |
OO |
AO |
BO |
AO, BO |
OO |
AO, OO |
BO, OO |
AO |
AA, AO |
AB, BO |
AA, AB, AO, BO |
AO, OO |
AA, AO, OO |
AO, BO, AB, OO |
BO |
AO, AB |
BB, BO |
AB, AO, BB, BO |
BO, OO |
AB, AO, BO, OO |
BB, BO, OO |
- AA = A blood type
- AO = A blood type
- BB = B blood type
- BO = B blood type
- OO = O blood type
- AB = AB blood type
Rh Factor
The Rh factor is simply a protein that is found on the covering of the red blood cells. If your red blood cells have this protein, you are Rh positive. If your blood cells don't have this protein, you are Rh negative.
Just as everyone inherits ABO genes, every person inherits one Rh factor gene from each parent. The Rh-positive gene is the dominant gene when paired with an Rh-negative gene.
Parent Genes |
Negative / Negative |
Positive / Postive |
Negative / Positive |
Negative / Negative |
Neg/Neg |
Neg/Pos |
Neg/Neg, Neg/Pos |
Positive / Positive |
Neg/Pos |
Pos/Pos |
Neg/Pos, Pos/Pos |
Negative / Positive |
Neg/Neg, Neg/Pos |
Neg/Pos, Pos/Pos |
Neg/Neg, Neg/Pos, Pos/Pos |
- Neg/Neg = Negative Rh factor
- Neg/Pos = Postive Rh factor
- Pos/Pos = Positive Rh factor