Inheritance
Blood groups are inherited from both parents. The ABO blood type is controlled by a single gene (the ABO gene) with three alleles: i, IA, and IB. The gene encodes a glycosyltransferase—that is, an enzyme that modifies the carbohydrate content of the red blood cell antigens. The gene is located on the long arm of the ninth chromosome (9q34).
The IA allele gives type A, IB gives type B, and i gives type O. As both IA and IB are dominant over i, only ii people have type O blood. Individuals with IAIA or IAi have type A blood, and individuals with IBIB or IBi have type B. IAIB people have both phenotypes, because A and B express a special dominance relationship: codominance, which means that type A and B parents can have an AB child. A type A and a type B couple can also have a type O child if they are both heterozygous (IBi,IAi) The cis-AB phenotype has a single enzyme that creates both A and B antigens. The resulting red blood cells do not usually express A or B antigen at the same level that would be expected on common group A1 or B red blood cells, which can help solve the problem of an apparently genetically impossible blood group.
Read more about this topic: ABO Blood Group System
Famous quotes containing the word inheritance:
“It is very difficult to be wholly joyous or wholly sad on this earth. The comic, when it is human, soon takes upon itself a face of pain; and some of our griefs ... have their source in weaknesses which must be recognized with smiling compassion as the common inheritance of us all.”
—Joseph Conrad (1857–1924)
“Say not you know another entirely till you have divided an inheritance with him.”
—Johann Kaspar Lavater (1741–1801)
“I call it our collective inheritance of isolation. We inherit isolation in the bones of our lives. It is passed on to us as sure as the shape of our noses and the length of our legs. When we are young, we are taught to keep to ourselves for reasons we may not yet understand. As we grow up we become the “men who never cry” and the “women who never complain.” We become another generation of people expected not to bother others with our problems.”
—Paula C. Lowe (20th century)