SEROLOGY AND SYSTEMATICS 



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The original purpose of the investigation was to discover, if 

 possible, the nature of the mechanism by which diploid pollen (from 

 tetraploids) carrying two different S alleles was not inhibited. If the 

 interaction fails to produce the "S-substances" or if a new product with 

 new specificity was produced under such circumstances, this might be 

 disclosed by the serological method. However, Lewis did not consider 

 the tests sensitive enough to yield vahd results. Linskins (1960) 

 reported results similar to those of Lewis in a study of three S alleles 

 in Petunia hybrids. It is obvious that methods analogous to those of 

 Lewis, and to some extent Irwin (that is, the gene homologies in 

 certain birds), might be apphed successfully to a study of gene 

 homology in related species. The critical point is to be able to pre- 

 adsorb in such a fashion as to leave in the antiserum a designated single 

 antibody which can then be used to screen other species. 



In the second example. Fox (1949) employed a serological 

 method to study specific eye color mutants of Drosophila. Using 

 isogenic stocks, he analyzed serologically various combinations of the 

 mutants, ruby and vermilion, along with the wild type. By means of 

 selective adsorption such as described above Fox showed that vermilion 

 antiserum and the double mutant, ruby-vermilion, antiserum were ser- 

 ologically equivalent. He inferred that the normal allele at the ruby 

 locus further modifies an "antigen" dependent upon the wild type 

 allele of vermilion. Therefore, in the presence of the vermilion allele 

 the normal allele at the ruby locus cannot effect the modification, and 

 consequently in the vermilion phenotype no serological difference be- 

 tween Rb (normal allele of ruby) and rb could be detected. If the 

 antigens are indeed enzymes and if the conclusions are valid, this 

 is yet another example of gene interaction to produce a single enzyme, 

 an exception to the classic one- gene, one-enzyme hypothesis. (Of course, 

 in these days, when the gene is becoming almost as difficult to define 

 as a species and virologists are threatening to reduce the "unit of 

 crossing-over" to as little as two nucleotide pairs (Benzer, 1957) such 

 aphoristic generalizations are inviting targets anyhow.) 



The examples just discussed do not by any means represent 

 all of the instances in which serological methods have been applied to 

 the study of specific enzymes or genetic factors. Several other studies 

 of this nature have been noted by Moritz (1958). 



In summary, there is reason to believe that serological tech- 

 niques, especially those utilizing immunogenetic methods (in general, 

 restricted to the lower taxonomic categories), will make important 

 contributions to systematics. Immunoelectrophoresis, however it may 

 be applied, presents in addition a distinct advance over earlier tech- 

 niques in that a qualitative element is introduced, and this technique 



