An inherited protein that can be found on the surface of the red blood cell. If your blood type is positive, then your blood cells have the Rh protein. If your blood type is negative, then your blood cells lack the Rh protein.
The Rh-positive gene is dominant when paired with an Rh-negative gene. If a person has the genes + +, the Rh factor in the blood will be positive. If a person has the genes + -, the Rh factor will also be positive.