scholarly journals The Responding Site of the Rex Locus of Drosophila melanogaster

Genetics ◽  
1987 ◽  
Vol 115 (2) ◽  
pp. 271-276
Author(s):  
Ellen E Swanson
Keyword(s):  
Drosophila Melanogaster ◽  
X Chromosome ◽  
Ribosomal Rna ◽  
Maternal Effect ◽  
Copy Number ◽  
Mitotic Chromosome ◽  
Gene Copy Number ◽  
Gene Copy ◽  
Rrna Gene ◽  
Chromosome Behavior

ABSTRACT Rex is a dominant, maternal-effect locus in the heterochromatin of the X chromosome Drosophila melanogaster. It causes an early mitotic exchange-like event between heterochromatic elements of an attached- XY in X/attached-XY embryos of Rex mothers. Evidence is presented here that the site of Rex action is the ribosomal RNA gene cluster (the bb locus) only; no other heterochromatin is affected. The Rex locus may be useful in studying regulation of rRNA-gene copy number, mitotic chromosome behavior and heterochromatic function.

scholarly journals Alteration of rRNA gene copy number and expression in patients with intellectual disability and heteromorphic acrocentric chromosomes

2018 ◽  
Vol 19 (2) ◽  
pp. 129-134 ◽  
Author(s):  
Irina S. Kolesnikova ◽  
Alexander A. Dolskiy ◽  
Natalya A. Lemskaya ◽  
Yulia V. Maksimova ◽  
Asia R. Shorina ◽  
...  
Keyword(s):  
Intellectual Disability ◽  
Copy Number ◽  
Gene Copy Number ◽  
Gene Copy ◽  
Rrna Gene ◽  
Acrocentric Chromosomes

scholarly journals Life History Implications of rRNA Gene Copy Number in Escherichia coli

2004 ◽  
Vol 70 (11) ◽  
pp. 6670-6677 ◽  
Author(s):  
Bradley S. Stevenson ◽  
Thomas M. Schmidt
Keyword(s):  
Escherichia Coli ◽  
Life History ◽  
Copy Number ◽  
Gene Copy Number ◽  
Rrna Operon ◽  
Relative Fitness ◽  
Gene Copy ◽  
Rrna Gene ◽  
Negative Consequences ◽  
Chemostat Cultures

ABSTRACT The role of the rRNA gene copy number as a central component of bacterial life histories was studied by using strains of Escherichia coli in which one or two of the seven rRNA operons (rrnA and/or rrnB) were deleted. The relative fitness of these strains was determined in competition experiments in both batch and chemostat cultures. In batch cultures, the decrease in relative fitness corresponded to the number of rRNA operons deleted, which could be accounted for completely by increased lag times and decreased growth rates. The magnitude of the deleterious effect varied with the environment in which fitness was measured: the negative consequences of rRNA operon deletions increased under culture conditions permitting more-rapid growth. The rRNA operon deletion strains were not more effective competitors under the regimen of constant, limited resources provided in chemostat cultures. Enhanced fitness in chemostat cultures would have suggested a simple tradeoff in which deletion strains grew faster (due to more efficient resource utilization) under resource limitation. The contributions of growth rate, lag time, Ks , and death rate to the fitness of each strain were verified through mathematical simulation of competition experiments. These data support the hypothesis that multiple rRNA operons are a component of bacterial life history and that they confer a selective advantage permitting microbes to respond quickly and grow rapidly in environments characterized by fluctuations in resource availability.

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