ADH, α-GPDH and SOD enzyme activities of second and third chromosomal genotypes from two geographically different populations of Drosophila melanogaster

ADH, α-GPDH and SOD enzyme activities have been measured in lines of Drosophila melanogaster homozygous and/or heterozygous for chromosomes extracted from two different populatioi Globally the results demonstrate that factors other than structural genes are determining the observed pattern of enzyme activities. ADH and α-GPDH activities are, however, more affected than SOD by these factors. Geographic origin, sex, chromosome, genetic background of the lines, containing regulatory genes in a broad sense, can be mentioned as the more relevant factors that influencing enzyme activities. A high and significant correlation is detected between ADH and α-GPDH enzyme activities and it can be interpreted as due to linkage disequilibrium among these two loci. SOD activity shows a lesser correlation with ADH and α-GPDH because it is less variable within population, i.e. it is a more canalized character. Finally, a principal component analysis, using the three enzyme systems shows that both populations are clearly separated, with a first principal component explaining 71.1 percent of the observed variance.