How many alleles are there for blood type

The variant may be recessive or dominant to the wild-type allele. An example of multiple alleles is the ABO blood-type system in humans.

In this case, there are three alleles circulating in the population. The I A allele codes for A molecules on the red blood cells, the I B allele codes for B molecules on the surface of red blood cells, and the i allele codes for no molecules on the red blood cells. In this case, the I A and I B alleles are codominant with each other and are both dominant over the i allele. Although there are three alleles present in a population, each individual only gets two of the alleles from their parents.

This produces the genotypes and phenotypes shown in the figure below. However, they can donate blood to people of any ABO blood type. However, they can donate blood only to people who also have type AB blood. ABO blood type antigens are found not only on red blood cells but also on platelets, in other body fluids such as tears and urine, and on cells of other types of tissues. Blood type compatibility is important to consider for successful organ transplantation.

If a transplanted organ has nonself antigens for ABO, it may be attacked by antibodies and rejected by the body. Another well-known blood group system is the Rhesus Rh blood group system. The Rhesus system has dozens of different antigens but only five main antigens named D, C, c, E, and e.

The major Rhesus antigen is the D antigen. Rhesus antigens are thought to play a role in transporting ions across cell membranes by acting as channel proteins. The Rhesus blood group system is controlled by two linked genes on chromosome 1. One gene, called RHD, produces a single antigen, antigen D.

The other gene, called RHCE, produces the other four relatively common Rhesus antigens C, c, E, and e , depending on which alleles for this gene are inherited. After the ABO system, the Rhesus system is the second most important blood group system in blood transfusions.

The D antigen is the one most likely to provoke an immune response in people who lack the antigen. Unlike anti-A and anti-B antibodies to ABO antigens, anti-D antibodies for the Rhesus system are not usually produced by sensitization to environmental substances. This may happen accidentally in a blood transfusion, although this is extremely unlikely today. This is especially likely if the mother has formed anti-D antibodies during a prior pregnancy because of a mixing of maternal and fetal blood during childbirth.

Unlike antibodies against ABO antigens, antibodies against the Rhesus D antigen can cross the placenta and enter the blood of the fetus. This may cause hemolytic disease of the newborn HDN , also called erythroblastosis fetalis, an illness in which fetal red blood cells are destroyed by maternal antibodies, causing anemia.

This illness may range from mild to severe. If it is severe, it may cause brain damage and is sometimes fatal for the fetus or newborn. Fortunately, HDN can be prevented by preventing the formation of anti-D antibodies in the Rh- mother. This is achieved through an injection into the mother of a medication called Rho D immune globulin.

Myth: Your nutritional needs can be determined by your ABO blood type. Knowing your blood type allows you to choose the appropriate foods that will help you lose weight, increase your energy, and live a longer, healthier life. Naturopathy is a method of treating disorders that involve the use of herbs, sunlight, fresh air, and other natural substances. Some medical doctors consider naturopathy a pseudoscience. A major scientific review of the blood type diet could find no evidence to support it.

In one study, adults eating the diet designed for blood type A showed improved health, but this occurred in everyone regardless of their blood type. Because the blood type diet is based solely on blood type, it fails to account for other factors that might require dietary adjustments or restrictions. For example, people with diabetes but different blood types would follow different diets, and one or both of the diets might conflict with standard diabetes dietary recommendations and be dangerous.

Myth: ABO blood type is associated with certain personality traits. There are two special blood types when it comes to blood transfusions. People with type O blood are universal donors because there are no molecules on the surface of the red blood cells that can trigger an immune response. People with type AB blood are universal recipients because they do not have any antibodies that will recognize type A or B surface molecules. Note: Blood cells are covered with a variety of surface molecules.

For simplicity, only type A and B surface molecules are shown here. Genes and Blood Type. Blood Types. Blood Type Is Determined Genetically. When Blood Types Mix. APA format:. Genetic Science Learning Center. Genes and Blood Type [Internet].