scholarly journals Computational Prediction of Position Effects of Human Chromosome Rearrangements

2018 ◽  
Vol 97 (1) ◽  
pp. e57
Author(s):  
Cinthya J. Zepeda-Mendoza ◽  
Shreya Menon ◽  
Cynthia C. Morton
Keyword(s):  
Human Chromosome ◽  
Computational Prediction ◽  
Chromosome Rearrangements ◽  
Position Effects

The effects of chromosome rearrangements on the expression of heterochromatic genes in chromosome 2L of Drosophila melanogaster.

Genetics ◽  
1990 ◽  
Vol 125 (1) ◽  
pp. 141-154 ◽  
Author(s):  
B T Wakimoto ◽  
M G Hearn
Keyword(s):  
Drosophila Melanogaster ◽  
Chromosome Rearrangements ◽  
Centromeric Heterochromatin ◽  
Chromosome 2 ◽  
Regulatory Requirement ◽  
Position Effects ◽  
Heterochromatic Genes

Abstract The light (lt) gene of Drosophila melanogaster is located at the base of the left arm of chromosome 2, within or very near centromeric heterochromatin (2Lh). Chromosome rearrangements that move the lt+ gene from its normal proximal position and place the gene in distal euchromatin result in mosaic or variegated expression of the gene. The cytogenetic and genetic properties of 17 lt-variegated rearrangements are described in this report. We show that five of the heterochromatic genes adjacent to lt are subject to inactivation by these rearrangements and that the euchromatic loci in proximal 2L are not detectably affected. The properties of the rearrangements suggest that proximity to heterochromatin is an important regulatory requirement for at least six 2Lh genes. We discuss how the properties of the position effects on heterochromatic genes relate to other proximity-dependent phenomena such as transvection.

scholarly journals Computational Prediction of Position Effects of Apparently Balanced Human Chromosomal Rearrangements

2017 ◽  
Vol 101 (2) ◽  
pp. 206-217 ◽  
Author(s):  
Cinthya J. Zepeda-Mendoza ◽  
Jonas Ibn-Salem ◽  
Tammy Kammin ◽  
David J. Harris ◽  
Debra Rita ◽  
...  
Keyword(s):  
Chromosomal Rearrangements ◽  
Computational Prediction ◽  
Position Effects

Epigenetics and the renaissance of heresy

Genome ◽  
2003 ◽  
Vol 46 (6) ◽  
pp. 963-967 ◽  
Author(s):  
Susannah Varmuza
Keyword(s):  
Dna Sequence ◽  
Driving Forces ◽  
Position Effect ◽  
Epigenetic Inheritance ◽  
Evolutionary Change ◽  
Chromosome Rearrangements ◽  
Phenotypic Change ◽  
Position Effects ◽  
Darwinian Theory ◽  
Richard Goldschmidt

Classic neo-Darwinian theory is predicated on the notion that all heritable phenotypic change is mediated by alterations of the DNA sequence in genomes. However, evidence is accumulating that stably heritable phenotypes can also have an epigenetic basis, lending support to the long-discarded notion of inheritance of acquired traits. As many of the examples of epigenetic inheritance are mediated by position effects, the possibility exists that chromosome rearrangements may be one of the driving forces behind evolutionary change by exerting position effect alterations in gene activity, an idea articulated by Richard Goldschmidt. The emerging evidence suggests that Goldschmidt's controversial hypothesis deserves a serious reevaluation.Key words: epigenetics, position effects, inheritance of acquired traits.

scholarly journals Position effect variegation in Drosophila melanogaster: relationship between suppression effect and the amount of Y chromosome.

Genetics ◽  
1989 ◽  
Vol 122 (4) ◽  
pp. 793-800 ◽  
Author(s):  
P Dimitri ◽  
C Pisano
Keyword(s):  
Drosophila Melanogaster ◽  
Y Chromosome ◽  
Position Effect ◽  
Chromosome Rearrangements ◽  
Position Effect Variegation ◽  
Position Effects ◽  
Suppression Effect ◽  
Genetic Nature ◽  
Cell Clones ◽  
Effect Variegation

Abstract Position effect variegation results from chromosome rearrangements which translocate euchromatic genes close to the heterochromatin. The euchromatin-heterochromatin association is responsible for the inactivation of these genes in some cell clones. In Drosophila melanogaster the Y chromosome, which is entirely heterochromatic, is known to suppress variegation of euchromatic genes. In the present work we have investigated the genetic nature of the variegation suppressing property of the D. melanogaster Y chromosome. We have determined the extent to which different cytologically characterized Y chromosome deficiencies and Y fragments suppress three V-type position effects: the Y-suppressed lethality, the white mottled and the brown dominant variegated phenotypes. We find that: (1) chromosomes which are cytologically different and yet retain similar amounts of heterochromatin are equally effective suppressors, and (2) suppression effect is positively related to the size of the Y chromosome deficiencies and fragments that we tested. It increases with increasing amounts of Y heterochromatin up to 60-80% of the entire Y, after which the effect reaches a plateau. These findings suggest suppression is a function of the amount of Y heterochromatin present in the genome and is not attributable to any discrete Y region.

On an Application of the Metallurgical Stage to Chromosome Morphology

1967 ◽  
Vol 25 ◽  
pp. 28-29
Author(s):  
Godfrey C. Hoskins
Keyword(s):  
Human Chromosome ◽  
Electron Micrographs ◽  
Chromosome Morphology ◽  
Electron Optics ◽  
Electron Micrograph ◽  
Photographic Evidence ◽  
Sophisticated Equipment ◽  
Periodic Arrangement

The first serious electron microscooic studies of chromosomes accompanied by pictures were by I. Elvers in 1941 and 1943. His prodigious study, from the manufacture of micronets to the development of procedures for interpreting electron micrographs has gone all but unnoticed. The application of todays sophisticated equipment confirms many of the findings he gleaned from interpretation of images distorted by the electron optics of that time. In his figure 18 he notes periodic arrangement of pepsin sensitive “prickles” now called secondary fibers. In his figure 66 precise regularity of arrangement of these fibers can be seen. In his figure 22 he reproduces Siegbahn's first stereoscopic electron micrograph of chromosomes.The two stereoscopic pairs of electron micrographs of a human chromosome presented here were taken with a metallurgical stage on a Phillips EM200. These views are interpreted as providing photographic evidence that primary fibers (1°F) about 1,200Å thick are surrounded by secondary fibers (2°F) arranged in regular intervals of about 2,800Å in this metanhase human chromosome. At the telomere the primary fibers bend back on themselves and entwine through the center of each of each chromatid. The secondary fibers are seen to continue to surround primary fibers at telomeres. Thus at telomeres, secondary fibers present a surface not unlike that of the side of the chromosome, and no more susceptible to the addition of broken elements from other chromosomes.

Impact of Comorbid Depression on Serial Position Effects in Alzheimer’s Disease

GeroPsych ◽  
2014 ◽  
Vol 27 (4) ◽  
pp. 161-169 ◽  
Author(s):  
Nienke A. Hofrichter ◽  
Sandra Dick ◽  
Thomas G. Riemer ◽  
Carsten Schleussner ◽  
Monique Goerke ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Serial Position ◽  
Episodic Memory ◽  
Memory Performance ◽  
Memory Function ◽  
Word List ◽  
Position Effects ◽  
Serial Position Effects ◽  
List Memory

Hippocampal dysfunction and deficits in episodic memory have been reported for both Alzheimer’s disease (AD) and major depressive disorder (MDD). Primacy performance has been associated with hippocampus-dependent episodic memory, while recency may reflect working memory performance. In this study, serial position profiles were examined in a total of 73 patients with MDD, AD, both AD and MDD, and healthy controls (HC) by means of CERAD-NP word list memory. Primacy performance was most impaired in AD with comorbid MDD, followed by AD, MDD, and HC. Recency performance, on the other hand, was comparable across groups. These findings indicate that primacy in AD is impaired in the presence of comorbid MDD, suggesting additive performance decrements in this specific episodic memory function.

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