What is RH factor?
Human blood consists of red cells – erythrocytes. In some cases, their surface contains antigens of group D, in such situations, talking about the positive RH. These substances are present in the blood approximately 85% of people, the remaining 15% negative RH factor, that is, they have these antigens are absent. In the blood there are other antigens, but their presence is not of such great importance in blood transfusion or pregnancy.
Transfusion of RH-positive blood to a person with a negative RH factor leads to the destruction of red blood cells, which causes the so-called pathological hemolysis – this is immune response to unfamiliar substances. People with a negative rhesus factor need to be taken when blood transfusion. You should also pay attention to their RH factor in pregnancy: RH negative mother and a positive father can cause rhesus incompatibility and lead to the development of hemolytic jaundice in the child, stillbirth or infant death.
RH positive people can receive blood from any RH factors, and pregnant women with this blood should not be afraid of conflict, even if the father is RH negative.
How is rhesus factor inherited?
The genes for RH factor are inherited according to the same principles as any other genes. So, when you inherit the dominant RH positive: in most cases, the "meetings" of the two genes responsible for different RH factors, wins the one who is responsible for positive. But not in all cases: even with a positive RH factor from both parents, a child may be born with a negative, but the probability of this is less. This happens because the alleles of the parents can attend different genes: one is dominant, causing a positive RH, and the other just exists but does not manifest itself. Since the formation of gametes alleles are divided into two parts, at the time of conception can meet the egg and sperm with the genes responsible for negative RH factor. In this case, and the child inherits the RH.
Clearly we can only assert that parents with negative RH-factor is going to be the same child as their genotype no gene responsible for the presence of antigens on erythrocytes. If one parent is RH negative and the second positive, then the child is equally likely to inherit one and the other.