Races of man / by Sonia Cole.

  • Sonia Mary Cole
Date:
1965
Catalogue details
    37/150 page 32
    Blood Groups and other Biochemical Characters Of all the inherited characters, only the blood groups have been studied in detail on a world-wide basis. This is not only because their method of inheritance is so simple, but also because of their importance in medicine5 since it was discovered that blood transfusions were effective only if blood of the right group was used, patients and donors have been 'typed' and data on blood groups now exist for millions of people from all parts of the world. The ABO Groups In the first years of the present century, Landsteiner discovered that human bloods could be tested to show four different groups: A, B, AB and 0. During the first world war, it was found that the frequencies of these groups varied con siderably in different populations. Since the ABO groups were distinguished and their genetics worked out in 1924, at least 10 other genetically independent systems have been found. The ABO groups are determined by the presence of a mucopolysaccharide (the antigen) on the red corpuscles of the blood. When red cells are mixed with the fluid part of the blood (serum) from an individual of a different group, the red cells become stuck together or agglutinated owing to the action of ABO antibodies in the serum. The mechanism of inheritance depends on three alleles and in theory six combinations are possible, producing six genotypes: AA, BB, AB, AO, BO, 00. But since 0 can only be distinguished in the homozygote 00, the heterozygotes AO and BO are indistinguishable from the homozygotes AA and BB. In fact, therefore, the combinations produce only four phenotypes: A, B, AB and 0. There 34
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