Genetic Control of enzyme synthesis

Chemical study of pyroxenes from the charnockitic rocks of Kondapalli (Andhra Pradesh), India, with emphasis, on the distribution of elements in coexisting pyroxenes

The chemical analyses, structural formulae, and trace element data are presented for 18 orthopyroxenes and 9 clinopyroxenes from the charnockitie rocks of Kondapalli, Andhra Pradesh, India. The chemistry of these pyroxenes is discussed and conclusions are drawn. The data are compared with the similar data available for the pyroxenes of the charnockites of the type area near Madras, some 200 miles south of Kondapalli. The element-distributional relationships between the coexisting pyroxenes are discussed and inferences are made regarding the temperature of crystallization of charnockite pyroxenes.

Simultaneous synthesis of histone and DNA in synchronously dividing Tetrahymena pyriformis

Histone and DNA syntheses have been studied in synchronously dividing Tetrahymena pyriformis GL. During the heat treatment necessary to synchronize cultures of this amicronucleate protozoan, the DNA content of the already polyploid macronucleus increases. When the cells begin synchronous division, their DNA content is reduced in a stepwise process which is closely paralleled by reduction of macronuclear histone content. During cell division, the contents of DNA and histone decrease by slightly more than twofold, and in the subsequent S phase, DNA and histone increase simultaneously to 85% of the values expected if all chromosomes were to double. The first step in the process of reduction of DNA and histone contents is their decrease in excess of twofold, and this is accomplished by removal of extrusion bodies from the nuclei of dividing cells. The second step is a mechanism which allows, in effect, only 70% of the chromatin in the average nucleus to duplicate. Such partial duplication suggests that both histone and DNA syntheses in synchronous Tetrahymena depend upon a regulatory mechanism, the mediating elements of which are localized in only certain chromosomes.

Effect of gene position on the timing of enzyme synthesis in synchronous cultures of yeast

Tauro, Patric (The University of Wisconsin, Madison), and Harlyn O. Halvorson. Effect of gene position on the timing of enzyme synthesis in synchronous cultures of yeast. J. Bacteriol. 92:652-661.-In synchronously growing cultures of Saccharomyces cerevisiae, enzyme synthesis is periodic. The effect of various factors on the timing of alpha-glucosidase synthesis has been investigated. The period of the cell cycle during which alpha-glucosidase is synthesized is unaffected by the method employed to induce synchrony, as well as other environmental conditions. However, a definite relationship exists between the number of nonallelic structural genes present for alpha-glucosidase and the number of periods of synthesis during the cell cycle. It is concluded that the periodic synthesis of enzymes observed in synchronously growing cultures of yeast is probably the result of an ordered process of transcription of the various structural genes.