SPECIFICITY OF GENE EFFECTS 255 



view, a pertinent question concerning tiiese antigenic complexes in cattle is 

 whether the cells which react with the B reagent, or with any other specific 

 reagent, do so by virtue of the presence of a specific reacting substance in a 

 single antigenic molecule, or otherwise? Does the comj)lex BOX, for exam])le, 

 represent (1) three different and separate antigenic substances? Or does it 

 represent (2) a single antigenic substance with (a) a possible common base 

 and three more or less different reactive groups accounting for B, G, and K, 

 respectively, or (6) a single substance capable of inciting many specificities of 

 antibodies, of which those for B, G, and K represent only a part of the re- 

 activities of the spectrum of antibodies which may be produced? A combina- 

 tion of (a) and (b) also may be a possibility. 



At present, very little experimental evidence is available concerning the 

 adequacy of any one or combination of the above possibilities to explain the 

 antigenic relationships of the components of the antigenic complexes of cattle 

 cells. Tests are under way to determine whether the reactive substance called 

 B, for example, is the same in all cells in which it appears, whether singly or 

 in an antigenic complex. 



In terms of the action of the causative genes, apart from the possibilities of 

 linkage and pseudo-allelism, the question seems to resolve itself around two 

 main aspects: (1) Do the genes controlling an antigenic complex, as a single 

 gene for BGK, have separate specificities for B, G, and K, or (2) does this 

 gene produce a single substance with no such separate specificities, and the 

 similarities between such a complex as BGK and BGIY, are due primarily if 

 not entirely to the general similarities in their chemical structure. The writer 

 is inclined to adopt a combination of these two possibilities as a current work- 

 ing hypothesis. No matter what may eventually prove to be the correct in- 

 terpretation of antigenic structure of the complexes, and the action of the 

 controlling genes, it appears that these studies have given some insight into 

 the complexities of the gene products and perhaps also of the causative genes. 



The studies of the specificities of the gene products — the antigens of the 

 blood cells of cattle — and the resulting inferences of the structure of the genes 

 themselves, may not be directly related to the over-all heterosis problem. 

 Nevertheless the writer is convinced that somewhat comparable specificities 

 might well be obtained in plants, in which attempts are currently in progress 

 to measure various aspects of the genetic bases for heterosis. Just how useful 

 an additional tool of this sort would he is only a guess. 



