Final answer:
The dominant (D) allele corresponds to the presence of the antigen D in the Rhesus blood group system, leading to an Rh positive status. The absence of the D antigen results in an Rh negative status, which may cause complications in Rh- mothers during subsequent pregnancies with Rh+ fetuses.
Step-by-step explanation:
The Rh antigen with the dominant (D) allele is critical in the Rhesus blood group system . People carrying this allele have the antigen D on the surface of their red blood cells, making them Rh positive (Rh+). Those lacking the D antigen are Rh negative (Rh-). The presence of the D antigen is particularly important during pregnancy; if an Rh- mother is carrying an Rh+ fetus, there is a risk of producing anti-Rh antibodies after the first pregnancy with an Rh+ fetus. These antibodies can cause issues in subsequent pregnancies with Rh+ fetuses, leading to hemolytic disease of the newborn , hence the preventive treatment with RhoGAM is recommended.