GENETICS OF SOMATIC CELLS 417 



group-0 child. Themosaicism was evidently inherited, since it was present in a younger 

 sister. In a second family, a similar + A 2 mosaic was found in mother and son. 

 One interesting case described by Armstrong et al. 3i was a person with true herma- 

 phroditism (testis on right side, ovary on left), having erythrocytes but a saliva 

 containing B substance in nearly normal quantity. 



The genetic control of antigenic specificity in higher organisms is a rather contro- 

 versial field and intensified studies on somatic blood-group variation may contribute to 

 the clarification of several issues. At present, it appears 985 that more than one locus 

 can affect an antigen, and a locus may affect more than one antigenic molecule. Also, 

 genetic variation may be concerned with haptenic substitutions at different sites of a 

 given macromolecular species. The development of refined techniques for the study 

 of somatic mutations, for example, in the Rh system, may help to illuminate the re- 

 lationships between genetic information and antigenic specificity and may resolve 

 the much-debated question of multiple alleles versus closely linked genes. 228, 985 

 Methodologic developments, specifically aiming at the detection and study of blood- 

 group mosaics, whether mutational or chimeric in origin, are of the greatest importance 

 for future advancement in this field. As one example of a promising approach, the 

 lytic system of Hildemann 574 in mice may be mentioned, as applied to the study of 

 artificial (radiation) chimeras by Owen. 982 This method permits the absolute 

 measurement in a spectrophotometer of the proportion of red cells hemolyzed by 

 isoantibody, directed against a given specific isoantigen, in the presence of complement. 

 Color caused by specific hemolysis can be compared with the color deriving from total 

 osmotic hemolysis of a similar test-cell suspension in distilled water. This proportion 

 of cells specifically hemolyzed in chimeric animals can be compared with (a) a similar 

 value for normal animals known to be positive to the test reagent or (b) mixtures 

 of known positive and negative suspensions of cells. According to Owen, 982 this 

 permits the quantitative evaluation of intermixtures in which the proportions of positive 

 cells range from about 5 to 100 per cent. Care must be taken, however, that the con- 

 centration of none of the reagents becomes limiting, with reference to the total number 

 of cells to be lysed. 



In addition to isoantigenic markers and chromosomal studies, genetic differences 

 in hemoglobin 1016 and a genetic deficiency leading to anemia 1100 have been useful in 

 studies on bone-marrow transplantation involving artificial chimerism. In the latter 

 case, normal and otherwise isologous marrow has been highly successful in competing 

 with anemic marrow. 



Among the many other phenomena interpreted as somatic mutations in normal 

 cells, straightforward genetic tests can be applied in exceptional cases where the mutated 

 sector involves both somatic and germinal tissue. In corn, for instance, a mutation 

 in the tassel can give rise to a sector that produces mutant pollen. The genetic nature 

 of this change can be confirmed by ordinary crosses. In animals, one particularly 

 interesting case has been reported by Russell and Major 1117 who studied the reversion of 

 the spontaneous color mutant pearl (pe) in mice to full color. Such reversions are 



