Spatial Heterogeneity of Certain Isoenzymes and Proteins

glucoso-6-phosphate will be mainly metabolized in glycolysis. This, in turn, will lead to the anaerobic biosynthesis of pentoses from glycolytic metabolites with the participation of transaldolase and transketolase enzymes. It is also possible that the lethal effect on the Pgd mutation is aggravated because the accumulation of 6-phosphogluconate is inhibitory to the first steps of glycolysis. Similar data were obtained by Hughes and Lucchesi (1977). 

Finally, the various interactions of genes were described at the post-transcrip-tional level for different stages of development. In some cases these relations between genes allowed a rough approximation of the action mechanisms of different gene-modifier groups. 

The complexity in this situation lies in that we cannot talk about the functional activity of separate genes (with rare exceptions) on the basis of individual mRNA production. The necessary methods have not been developed, therefore in experimental genetics indirect methods based on final product determinations are used. 

What is known of the transcription process during ontogenesis allows the suggestion of the presence of temporal and spatial differences in the phenotypic expression of biochemical traits. A large amount of data, obtained mainly by electrophoretic and immunochemical methods, has confirmed this suggestion. 

The investigation of isozyme changes during ontogenesis at the organ, tissue, and cellular levels began to be widespread after their discovery by Markert (Hunter and Markert, 1957). 

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