Blood and History

[Cheba_Mami]

January 16, 2007
Is there an evolutionary reason for human blood types?


by Victoria Roberts
A. The blood types classified as A, B, AB and O appeared and predominated in geographically separated populations over the course of human history, and it has been assumed that the differences conferred some biological advantage. A recent suggestive study links this advantage to how different kinds of infections, bacterial and viral, interact with different blood types.

The study, by researchers at University College, London, appeared in 2004 in the Proceedings of the Royal Society.

Blood types are characterized by certain complex sugars, with the types differing genetically. When the sugars end up on the surfaces of cells, they determine how the body and an invader interact.

The researchers’ statistical model found that the rates of occurrence of these blood types closely mirrored the distribution of opportunistic bacterial infections, which are best fought off by A and B blood types, and the distribution of viral infections, which are best fought off by O blood types.

The researchers said they hoped the study could point the way to a better understanding of how the changing influenza virus could be fought off by the immune system.

[Bent_Bladi]

wow! how interesting... thanks for sharing ChM (haha, like PhD )

[Cheba_Mami]

Thanks BB, ill get that one day the chM degree
Basic info:

What are Blood Types?

Everybody has a blood type. The most common blood type classification system is the ABO (say "A-B-O") system discovered by Karl Landsteiner in the early 1900s. There are four types of blood in the ABO system: A, B, AB, and O. Your blood type is established before you are born, by specific genes inherited from your parents. You receive one gene from your mother and one from your father; these two combine to establish your blood type. These two genes determine your blood type by causing proteins called agglutinogens (a-GLOO-tin-a-gins) to exist on the surface of all of your red blood cells.

There are three alleles or versions of the blood type gene: A, B, and O. Since everybody has two copies of these genes, there are six possible combinations; AA, BB, OO, AB, AO, and BO. In genetic terms, these combinations are called genotypes, and they describe the genes you got from your parents.

In addition to the proteins (agglutinogens) existing on your red blood cells, other genes make proteins called agglutinins (a-GLOO-tin-ins) that circulate in your blood plasma. Agglutinins are responsible for ensuring that only the blood cells of your blood type exist in your body.

Your genotype determines your blood type.
The agglutinogen produced by the O allele has no special enzymatic activities. However, the agglutinogens produced by the A and B alleles do have enzymatic activities, which are different from each other. Therefore people whose genotype is OO are said to have type O blood, meaning the agglutinogen on their red blood cells doesn't have any enzymatic activity. People with Type O blood have agglutinins a and b in their blood plasma. Agglutinin a helps the body destroy any type A blood cells that might enter the circulation system. Agglutinin b helps the body destroy any type B blood cells that might enter the circulation system.


People who have an AA genotype are said to have type A blood because the agglutinogen on their red blood cells has the enzyme activity associated with the A allele. It is important to recognize that people with the AO genotype also have the enzyme activity associated with the A allele, so they are also said to have type A blood. (Remember the O allele doesn't have any enzyme activity associated with it!) People with Type A blood have agglutinin b in their blood plasma. Agglutinin b helps the body destroy any type B blood cells that might enter the circulation system.

Likewise, people with the BB and the BO genotypes are said to have type B blood. These people have agglutinin a in their blood plasma. Agglutinin a helps the body destroy any type A blood cells that might enter the circulation system.

People who have the AB genotype have the enzyme activity associated with both the A and B alleles. These people have no agglutinins in their blood plasma.

The concepts of genotype and phenotype can be easily understood in the case of blood type. Genotype refers the actual genes an individual possesses that determine a particular trait. Phenotype refers to the characteristics of that trait an individual displays. In the case of blood type, both the AA and AO genotypes cause individuals to display the A blood type phenotype. Similarly, both the BB and BO genotypes cause individuals to display the B blood type phenotype. Individuals who are phenotypically type O or type AB have only one possible genotype, OO and AB, respectively.

In different parts of the world, the fraction of individuals with blood type A, B, O, or AB differs. The frequency with which blood types are observed is determined by the frequency with which the three alleles of the ABO gene are found in different parts of the world (allele frequency). Variation in the allele frequency at the ABO gene reflects the social tendency of populations to marry and reproduce within a national, regional, or ethnic group. As people throughout the world intermingle to a greater extent, the distribution of the different blood types will become more uniform throughout the world.

What are Blood Types?

p.s. Know your bloodtype in case of emergency/ when you need quickly a blood supply.

[Cheba_Mami]

[Bent_Bladi]

wow... i wish i had that chart a few months ago.... . and iwli, I need to find out what my blood type is... 17 years and no one has told me ~~~

[Cheba_Mami]

Distribution of bloodtypes:

= Type O
= type B
= Type A

[Bent_Bladi]

Hmmm, then maybe I'm an O......