The A-B Blood Groups in Human Beings 285 



tinogen A and a second dominant allele results in the production 

 of agglutinogen B. Neither of these two dominant genes is 

 dominant over the other. 



Several systems of symbols have been used by various scien- 

 tists to designate these alleles. The early theory of Bernstein 

 used to represent the gene that resulted in no agglutinogen, 

 A for the gene producing agglutinogen A, and B for the gene 

 for agglutinogen B. Thus, the three alleles are 0, A, and B. 

 This system is adequate, but is not in conformity with the usual 

 system of genetic nomenclature, according to which all genes at 

 a given locus have the same symbol except for the use of a 

 capital or lower-case form to designate dominance or recessive- 

 ness, or for the plus sign which indicates the wild type, and 

 except for the addition of different superscripts to indicate the 

 various members of a series of multiple alleles. In an attempt 

 to have the genes for the blood groups conform to this system, 

 some authors use a for Bernstein's 0, and a^ for his B. This 

 system is an improvement but would tend to suggest that gene 

 A was the top dominant in the series whereas it is not dominant 

 over a^. Another system assumes that group is the wild type 

 or standard and uses a plus sign to indicate Bernstein's gene 0, 

 retaining the symbols A and B. Another method, and one which 

 is in harmony with genetic practice, was suggested by Strands- 

 kov. He suggests the symbol i for the gene for no isoagglutino- 

 gen and I"^ and I^ for the dominant genes producing agglutino- 

 gens A and B respectively. AVithout passing on the merits of 

 the various systems, the early system of 0, A, and B will be 

 adopted for this book because it is so widely used by the active 

 workers in the field. Because it is so formally correct, the sym- 

 bols of Strandskov will also be indicated in many places. 



Disregarding the subgroups which will be mentioned later, 

 individuals of group will be genotypicalh^ 00 (or ii). Those 

 of group A will be AO or .4.4 {7-^/ or h^I^) and those of group 

 B will have the genotypes BB {PP) or BO {IH). Genes .4 and 

 B (/^ and I^) show no dominant and recessive relationship with 

 respect to one another. If an individual is genotypically AB 

 (I^I^), he possesses both agglutinogens and therefore belongs 

 to group AB. 



If blood from a group A person is injected into people of 

 groups A or AB, no harmful consequences arise because such 



