Showing papers on "Dosage compensation published in 1972"
TL;DR: Dosage compensation seems to increase the transcription rate of mRNA on the male-X while not increasing the synthesis of non-messenger chromosomal RNA.
Abstract: Autoradiographs of 3H-uridine pulse labeled Drosophila melanogaster salivary gland polytene chromosomes were prepared from normal genotypes and from genotypes which contained either an intrachromosomal duplication of region 16A-17E of the X-chromosome or a non-reciprocal translocation of this segment. RNA extracted from these cytological preparations showed an electrophoretic profile similar to that of RNA from gland homogenates. Silver grains were scored over individual bands. Two different methods to correct for geometry and self-absorption were used to determine the 3H-RNA content of each band. Instability of a band's transcription rate increased with gene dose. The average transcription rate per unit DNA was generally independent of gene dose (dosage effect or additivity). Pairing of homologous bands suppressed RNA synthesis in band 17B. One sex-linked gene in a male or two sex-linked genes in a female effect the same enzyme levels (dosage compensation). Any one X-chromosome band in a male was found to transcribe 0.7 units of RNA for each 1.0 units transcribed by two similar bands in a female-X. Thus, a 40% increase in RNA synthesis by male-X bands effects a 100% increase in enzyme levels. Dosage compensation seems to increase the transcription rate of mRNA on the male-X while not increasing the synthesis of non-messenger chromosomal RNA.
34 citations
TL;DR: This study has obtained further and more rigorous proof that late replication of the X chromosome corresponds to genetic inactivation at the G-6-PD locus, and obtained data bearing on the problem of the postulated randomness of inactivation.
Abstract: IN the female mule (Equus caballus × E. asinus), the horse (maternal) and the donkey (paternal) X chromosomes are morphologically distinguishable1,2, and the X-linked enzyme, glucose-6-phosphate dehydrogenase (G-6-PD), is present as a combination of the two electrophoretically distinct parental forms3,4. Female mule cells therefore may serve as an experimental model for the simultaneous study of both cytological and biochemical aspects of dosage compensation for X-linked loci in mammals (Lyon hypothesis5). We have demonstrated a very close correlation between late replication of either one or the other of the parental X chromosomes, and relative activity of the complementary form of G-6-PD6. In this study we have obtained further and more rigorous proof that late replication of the X chromosome corresponds to genetic inactivation at the G-6-PD locus. We have also obtained data bearing on the problem of the postulated randomness of inactivation.
25 citations
01 Jan 1972
TL;DR: Despite the changes in the configuration and organization of the X-chromosome in these species, the hyperactivity of the male X and therefore, dosage compensation for X-linked genes, has remained unchanged.
Abstract: The functional morphology and the transcriptive activity of the male X-chromosome in Drosophila kikkawai and D. bipectinatahave been exarnined. In both these species of the melanogaster species-group, the X-chromosome in the salivary glands of the male Iarvae is enlarged and pale stained as in Drosophila melanogaster, 3 H-uridine autoradiography shows that in both the species, the relative rate of RNA synthesis by the single X of the male is similar to that by the two X's of female. The results indicate that: (a) the enlargement and pale staining of the single X in the larval salivary glands of [he male is of general occurrence in the genus Drosophila, and (b) despite the changes in the configuration and organization of the X-chromosome in these species (that have taken place during their evolution), the hyperactivity of the male X and therefore, dosage compensation for X-linked genes, has remained unchanged.
10 citations
01 Dec 1972
TL;DR: The three principal attributes of Drosophila polytene X-chromosome in male, increased wodth, high rate of RNA sythesis and faster DNA replication, are probably casually interdependent and related to genetic dosage compensation.
Abstract: The three principal attributes of Drosophila polytene X-chromosome in male namely, increased wodth, high rate of RNA sythesis and faster DNA replication, are probably casually interdependent and related to genetic dosage compensation (see Lakhotia and Mukherjee 1970) A direct demonstration of this relationship is not possible from studies on the normal glands However, an approach in this direction may be made since under certain circumstances like X-irradiation of larvae, the width of male X is reduced to approximate that of the asynapsed X's of female nuclei (Lakhotia 1970a; Mukherjee et al 1968) In the present paper some aspects of the alterations induced in the transcriptive and replicative organization of the male X following X-irradiation of late third instar larvae D melanogaster will be presented, a preliminary account having been presented eralier (Lakhotia 1971)
6 citations