9g BIOCHEMICAL SYSTEMATICS 



on the basis of the evidence presented, certainly no clear-cut dif- 

 ferences can be detected. 



On the basis of previous results and on theoretical grounds, 

 differences such as those reported are indeed surprising, though 

 Buzzati-Traverso did not indicate this to be so. For example, Hadorn 

 and Mitchell did not detect differences in the heterozygote, and those 

 authors were studying biochemical mutants.2 in the Buzzati-Traverso 

 work in which a series of morphological mutants were compared, it is 

 remarkable that of a small number of unidentified fluorescent sub- 

 stances, one or more of them are invariably affected, quantitatively or 

 qualitatively by each mutation. It is even more surprising that the 

 heterozygotes could be detected chromatographically. In general when 

 a biochemical mutant is dominant (for example, a flower color factor) 

 one can scarcely detect the heterozygote even by sensitive quantitative 

 methods. Dominance may be above 90 per cent in the majority of 



such cases. 



Similarly Buzzati-Traverso reported that a recessive mutant 

 of tomato had two fluorescing spots not present in the wild type strain. 

 However, in this case the fluorescent pattern of the heterozygote was 

 similar to that of the double recessive, but its ninhydrin pattern was 

 intermediate. Finally, in a yellow-green mutant of muskmelon the 

 chlorophyll content of the heterozygote could not be distinguished 

 from the homozygous dominant, but the ninhydrin pattern of the 

 heterozygote was indistinguishable from that of the double recessive. 

 The writers consider that the interpretation given by Buzzati-Traverso 

 to his results is not necessarily the only interpretation which is 

 plausible, since the photographs resemble closely anomalies we have 

 sometimes observed in our experiences with paper chromatography. 



Interesting work on the comparative fluorescent patterns of 

 male and female Drosophila has been reported by Fox (1956). He was 

 principally concerned with whether any biochemical differences could 

 be attributed to the presence of the Y chromosome. Therefore, he 

 compared males and females chromatographically and then compared 

 normal (XX) females and females carrying, in addition, a Y chromo- 

 some (XXY). These two types of females showed similar patterns, 

 suggesting that the Y chromosome itself was not responsible for 

 any overt biochemical effect. Of more significance to systematic in- 

 vestigations was the disclosure by Fox that, in isogenic stocks, strik- 

 ing differences in the fluorescent patterns of males and females 

 occurred. Ten spots were common to males and females, but in all 



2 In the case of white eye, which is morphologically recessive, the chromatographic 

 pattern of the heterozygote is distinguishable from the homozygote of either class, but 

 this appears to be rather exceptional (Hadorn, 1962). 



