300 BIOCHEMICAL SYSTEMATICS 



half the concentration found in the parents. This result implies a pos- 

 sible relationship between components A and B and would, therefore, 

 justify further comparative study of these components. Nevertheless, 

 Schwartz (1960) has presented what seems to be unequivocal evidence 

 for the presence of a hybrid protein in maize. This work relates 

 to several questions of rather fundamental nature. The method, rela- 

 tively simple, involves a separation of enzymes from the tissue con- 

 cerned (crude extracts from endosperm, for example) by means of 

 starch gel zone electrophoresis. Esterases, which were the type of 

 enzyme studied, were then visualized by treating with a substrate 

 such as a-naphthyl acetate and a dye coupler. 



Using different inbred genetic lines three different forms of 

 basic protein with esterase activity were detected and designated as 

 follows: S = slow moving esterase, N = normal esterase (most com- 

 monly found, with intermediate migration rate), and F = fast moving 

 esterase. The inbred lines contained either S, N, or F. When artificial 

 mixtures were utilized, no interaction occurred, and the individual 

 bands appeared without the formation of new bands. 



When genetic lines with differing esterase components are 

 crossed, the hybrids produce both parental esterase types and 

 invariably a "hybrid esterase" running at an intermediate rate (Fig. 

 15-1). Furthermore when the hybrid between N and S was selfed, the 

 F2 progeny segregated as follows: 



Thirty-two contained N. 



Fifty-five contained N, S, and hybrid esterase. 



Thirty-six contained S. 



1 



ab cd ef gh 



Fig. 15-1. Zymograms of endosperm extracts showing the various 

 esterase types; a, slow; b, normal; c, fast; d, mixture of normal and 

 slow; e, mixture of normal and fast; f, mixture of fast and slow; g, 

 N X F <5 hybrid; h, N x S S hybrid. (Schwartz, 1960). 



