The two molecular weight forms of rat phenylalanine hydroxylase are encoded by different messenger RNAs

Immunoprecipitation of the phenylalanine hydroxylase formed by translation of rat liver RNA in a rabbit reticulocyte cell-free protein synthesis system was used to examine the origin of the molecular weight heterogeneity of the enzyme. Sodium dodecyl sulfate-polyacrylamide electrophoresis of the immunoprecipitated products showed that in most cases a single specifically immunoprecipitated polypeptide was produced which corresponded to the higher molecular weight (H) form of phenylalanine hydroxylase (Mr = 50,000). The identity of the product was confirmed by immunological competition and peptide mapping. RNA from other rats, however, coded for both the H-form and the lower molecular weight (L) form of phenylalanine hydroxylase or for only the L-form. The evidence suggests that the L-form derives from a different mRNA, rather than by proteolysis of the H-form, an interpretation which is supported by the isolation of the lower form of phenylalanine hydroxylase from livers of some rats.     

Chemical composition and ultrastructure of the epicuticular wax in four mutants of Pisum sativum (L)

The action of mutations affecting the epicuticular wax of Pisum sativum has been investigated at the chemical and ultrastructural level. Upper and lower surfaces of the leaves were found to differ markedly in both ultrastructure and chemistry. Mutations affected primarily either the lower (wa, wb and wsp) or the upper surface (wlo), but some effects of all 4 genes could be seen on both surfaces. Specific biochemical lesions could be implied for wsp and wa but the chemical effects of wb and wlo were more diffuse. Generally a close relation between chemical composition and crystallite form of the wax was evident throughout the work.     

Molecular evolution in Hawaiian drosophilids

The evolutionary relationships of the Hawaiian drosophilids have been studied by several molecular techniques. Immunological measurements have determined some of the distances between the major groups. More detailed studies have used protein polymorphism, DNA hybridization, DNA restriction enzyme analysis and DNA sequence studies of both nuclear and mitochondrial genomes. These studies indicate both the strengths and the weaknesses of the various methods and suggest new ways to examine phylogenetic relationships and question some of the accepted ph ylogenies.