What Is the Origin of Blood Type A?

Blood types can be classified into a number of genetically differentiated types, which permits the study of human genetic and biological variation without the negative aspects of cultural prejudice. Just a century ago, no one was aware of his blood type, even today many people are unaware of their own blood type. Every human population throughout the world shares the same 27 known blood type systems, though certain types are prevalent in each group.

• Blood cells

Who Has Blood Type A?

• Around 21 percent of all humans share the type A blood allele. The greatest prevalence of type A occurs in small and unrelated population groups like Montana's Blackfoot Indians (30 to 35 percent), Australia's Aborigines (40 to 53 percent) and the Lapps, who originate in Northern Scandinavia (50 to 90 percent).

Type A and Blood Donations

• In the past blood type O was considered suitable for donation to recipients with any blood type. Blood type O donors were called "'universal donors." Because of new research and a better understanding of blood and plasma, today we know that this is not the case. The type of blood you can receive depends on whether you are getting whole blood, red cells, or plasma.

Significance

• The letters in a blood type represent antigens. Blood type A has the A antigen. Someone with blood type A has one or two parents with type A blood, but one parent could have type O blood. Blood type A is the second most common type (after O). According to the American Red Cross, 40 percent of white people, 26 percent of African-Americans, 31 percent of Hispanics and 28 percent of Asians have this blood type.

Alleles

• The term allele comes from the Greek word "allelos" which means "other." The word is short for allelomorph, meaning "other form." It refers to different variants of a gene. We each inherit a range of alleles that make us unique. The specific combination of alleles that contribute to your shape, size, personality and other characteristics is known as the genotype.

Antigens

• Blood types are a result of different antigens on the red blood cell's surfaces. Antigens are chemicals that initiate the production of antibodies. Blood cell antigens develop from a precursor known as H substance. While antigens are found on the cell's surface, antibodies are found in the blood plasma. The differences between human blood types are a result of either the presence or absence of specific antigens and antibodies. Which type and combination of theses molecules you have depends on what you inherited from your parents.