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:
“Late in the afternoon we passed a man on the shore fishing with a long birch pole.... The characteristics and pursuits of various ages and races of men are always existing in epitome in every neighborhood. The pleasures of my earliest youth have become the inheritance of other men. This man is still a fisher, and belongs to an era in which I myself have lived.”
—Henry David Thoreau (1817–1862)
“A child is born with the potential ability to learn Chinese or Swahili, play a kazoo, climb a tree, make a strudel or a birdhouse, take pleasure in finding the coordinates of a star. Genetic inheritance determines a child’s abilities and weaknesses. But those who raise a child call forth from that matrix the traits and talents they consider important.”
—Emilie Buchwald (20th century)
“A slave who deals wisely will rule over a child who acts shamefully, and will share the inheritance as one of the family.”
—Bible: Hebrew, Proverbs 17:2.