scholarly journals Evaluation of the mutagenic potential of propoxur and methyl parathion using polytene chromosomes of Anopheles stephensi

2012 ◽  
Vol 4 (1) ◽  
pp. 79-84
Author(s):  
Asha Chaudhry ◽  
Preety Bhinder ◽  
Ram Kumar ◽  
Ravneet Kaur
Keyword(s):  
X Chromosome ◽  
Methyl Parathion ◽  
Anopheles Stephensi ◽  
Polytene Chromosomes ◽  
Mutagenic Potential ◽  
X Chromosomes ◽  
Structural Aberrations ◽  
Ectopic Pairing ◽  
Pesticide Genotoxicity

The mutagenicity of two pesticides, propoxur and methyl parathion was evaluated by using polytene chromosomes of Anopheles stephensi. The results were based on the frequency of various structural aberrations encountered in the polytene chromosomes of the larvae treated with LC20 of propoxur and methyl parathion separately. Propoxur induced a total of 67 aberrations as against 15 in the controls while methyl parathion induced 53 aberrations as against 13 in the controls. These aberrations were dominated by inversions, translocations, deletions, ectopic pairing, asynapses, breaks, fusions and induced puffing. The frequency of propoxur induced aberrations was highest in chromosome 3R followed by 2R, 3L, 2L and X-chromosome. Methyl parathion induced highest number of aberrations in 2R followed by 2L, 3R, 3L and X-chromosomes. This study suggests that larval polytene chromosomes are sensitive indicators of pesticide genotoxicity in which both propoxur and methyl parathion are significantly chromotoxic for the genome of a mosquito taken as an experimental insect.

Polytene and mitotic chromosome analysis in Ceratitis capitata (Diptera; Tephritidae)

1986 ◽  
Vol 28 (2) ◽  
pp. 180-188 ◽  
Author(s):  
D. G. Bedo
Keyword(s):  
X Chromosome ◽  
Silver Staining ◽  
Mitotic Chromosome ◽  
Ceratitis Capitata ◽  
Fat Body ◽  
Polytene Chromosomes ◽  
Chromosome Analysis ◽  
Mitotic Chromosomes ◽  
Chromosome Separation ◽  
Ectopic Pairing

Polytene chromosomes were found in several larval and pupal tissues of the Medfly, Ceratitis capitata, during a search for chromosomes suitable for detailed cytological analysis. Well-banded highly polytene chromosomes, which could be adequately separated and spread, were found in trichogen cells of the spatulate superior orbital bristles of male pupae. These chromosomes proved suitable for full polytene analysis. Thoracic trichogen cells of both male and female pupae also contain useful polytene chromosomes, although they are considerably thinner and thus more difficult to analyze. Contrasting with those in pupal trichogen cells, the chromosomes in the salivary glands, Malphighian tubules, midgut, hindgut, and fat body of larvae and pupae were difficult to prepare because of high levels of ectopic pairing and chromosome fragmentation. In hindgut preparations partial separation of up to three chromosomes was achieved, but in all other tissues no useful chromosome separation was possible. In trichogen polytene cells, five banded chromosomes and a prominent heterochromatic network associated with a nucleolus are found. The mitotic chromosomes respond to C- and Q-banding and silver staining with considerable variation. This is especially so in the X chromosome, which displays an extensive array of bands following both Q-banding and silver staining. Comparison of Q-banded metaphase and polytene chromosomes demonstrates that the five autosomes are represented by conventional polytene chromosomes, while the sex chromosomes are contained in the heterochromatic net, most of which fluoresces strongly. This suggests that the Q-bands of the mitotic X chromosome are replicated to a greater extent than the nonfluorescent material in polytene cells. This investigation shows C. capitata to have excellent cytological material for both polytene and mitotic analysis.Key words: Ceratitis capitata, Medfly, chromosomes (polytene), banding (chromosome).

XV.—“Ectopic” Pairing and the Distribution of Heterochromatin in the X-Chromosome of Salivary Gland Nuclei of Drosophila melanogaster

1946 ◽  
Vol 62 (2) ◽  
pp. 114-119 ◽  
Author(s):  
B. M. Slizynski
Keyword(s):  
Drosophila Melanogaster ◽  
Salivary Gland ◽  
Nucleic Acid ◽  
X Chromosome ◽  
Polytene Chromosomes ◽  
Ectopic Pairing

The problem to be presented here emerges from the following groups of facts and more or less generally accepted opinions.As heterochromatin we may define those parts of chromosomes which reach maximum nucleic acid charge in mitosis or meiosis in times other than metaphase. In salivary gland chromosomes (which are more conveniently called polytene chromosomes) of Drosophila melanogaster the proximal heterochromatic parts of all chromosomes come together and form a central undifferentiated mass, the chromocentre. Genetically heterochromatin forms the so-called inert regions of the chromosomes.

scholarly journals IN SUPPORT OF THE TELOMERE CONCEPT

Genetics ◽  
1975 ◽  
Vol 80 (1) ◽  
pp. 135-142
Author(s):  
Paul A Roberts
Keyword(s):  
Drosophila Melanogaster ◽  
X Chromosome ◽  
Mitotic Chromosome ◽  
Polytene Chromosomes ◽  
Metaphase Chromosomes ◽  
X Chromosomes ◽  
X Ray ◽  
Single Exception

ABSTRACT The frequency of recovered X-ray-induced (4000R) rearrangements that, in all probability, mimic terminal deletions of the X chromosome was only one of, roughly, 105  X chromosomes screened for tip deficiencies. Although the single exception looks terminally deleted, it is probably capped by a very short or nonpolytene telomeric segment. It is apparent from these data that the probability of "healing" or stabilization of a terminally deleted X in the zygotic nucleus or developing embryo of Drosophila melanogaster is vanishingly small. The telomeric caps in two obviously interstitial deficiencies that were recovered represent, roughly, 1/500 of the length of a mitotic chromosome. These findings give some indication of the extreme difficulty of detecting short telomeric segments capping either deleted polytene chromosomes or deleted metaphase chromosomes of, for example, humans.

scholarly journals The three-dimensional organization of polytene nuclei in male Drosophila melanogaster with compound XY or ring X chromosomes.

Genetics ◽  
1989 ◽  
Vol 121 (2) ◽  
pp. 293-311
Author(s):  
D Mathog ◽  
J W Sedat
Keyword(s):  
Drosophila Melanogaster ◽  
Salivary Glands ◽  
X Chromosome ◽  
Genetic Regulation ◽  
Polytene Chromosomes ◽  
Three Dimensional ◽  
X Chromosomes ◽  
Frequent Failure ◽  
Polytene Nucleus ◽  
Polytene Nuclei

Abstract The three-dimensional organization of polytene chromosomes within nuclei containing rearranged X chromosomes was examined in male Drosophila melanogaster. Salivary glands of third instar larvae containing either an inverted X chromosome (YSX.YL, In(1)EN/O) or a ring X chromosome (R(1) 2/BSYy+) were fixed, embedded, and serially sectioned. The nuclei in contiguous groups of cells were modeled and analyzed. We find that for both genotypes the three-dimensional behavior at each euchromatic locus is independent of the orientation of the chromosome on which it resides, independent of the behavior of loci not closely linked to it, and not similar in neighboring cells. The preference for right-handed chromosome coiling noted in previous studies is shown to be independent of homologous pairing. However, a relation between the extent of chromosome curvature and the handedness of chromosome coiling is present only in homologously paired chromosomes. The attached-XY chromosome has two previously undescribed behaviors: a nearly invariant association of the euchromatic side of the proximal heterochromatin/euchromatin junction with the nucleolus and a frequent failure of this site to attach to the chromocenter. The relative chromosome arm positions are often similar in several neighboring cells. The size of these patches of cells, assuming that they represent clones, indicates that such arrangements are at best quasi-stable: they may be maintained over at least one, but less than four, cell divisions. The observed nuclear organization in salivary glands is inconsistent with the idea that position in the polytene nucleus plays a major role in the normal genetic regulation of euchromatic loci.

scholarly journals Bisection of the X chromosome disrupts the initiation of chromosome silencing during meiosis in Caenorhabditis elegans

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yisrael Rappaport ◽  
Hanna Achache ◽  
Roni Falk ◽  
Omer Murik ◽  
Oren Ram ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Rna Polymerase Ii ◽  
X Chromosome ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Transcription Analysis ◽  
X Chromosomes ◽  
Unique Character ◽  
Active Transcription ◽  
Heterogametic Sex

AbstractDuring meiosis, gene expression is silenced in aberrantly unsynapsed chromatin and in heterogametic sex chromosomes. Initiation of sex chromosome silencing is disrupted in meiocytes with sex chromosome-autosome translocations. To determine whether this is due to aberrant synapsis or loss of continuity of sex chromosomes, we engineered Caenorhabditis elegans nematodes with non-translocated, bisected X chromosomes. In early meiocytes of mutant males and hermaphrodites, X segments are enriched with euchromatin assembly markers and active RNA polymerase II staining, indicating active transcription. Analysis of RNA-seq data showed that genes from the X chromosome are upregulated in gonads of mutant worms. Contrary to previous models, which predicted that any unsynapsed chromatin is silenced during meiosis, our data indicate that unsynapsed X segments are transcribed. Therefore, our results suggest that sex chromosome chromatin has a unique character that facilitates its meiotic expression when its continuity is lost, regardless of whether or not it is synapsed.

scholarly journals DNA methylation and behavioral dysfunction in males with 47,XXY and 49,XXXXY: a pilot study

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Richard S. Lee ◽  
Sophia Q. Song ◽  
Henri M. Garrison-Desany ◽  
Jenny L. Carey ◽  
Patricia Lasutschinkow ◽  
...  
Keyword(s):  
Pilot Study ◽  
X Chromosome ◽  
Child Behavior Checklist ◽  
Epigenetic Modification ◽  
Cpg Methylation ◽  
Monoamine Oxidase A ◽  
Low Fertility ◽  
X Chromosomes ◽  
Behavioral Dysfunction ◽  
Study Results

Abstract Background Equal dosage of X-linked genes between males and females is maintained by the X-inactivation of the second X chromosome in females through epigenetic mechanisms. Boys with aneuploidy of the X chromosome exhibit a host of symptoms such as low fertility, musculoskeletal anomalies, and cognitive and behavioral deficits that are presumed to be caused by the abnormal dosage of these genes. The objective of this pilot study is to assess the relationship between CpG methylation, an epigenetic modification, at several genes on the X chromosome and behavioral dysfunction in boys with supernumerary X chromosomes. Results Two parental questionnaires, the Behavior Rating Inventory of Executive Function (BRIEF) and Child Behavior Checklist (CBCL), were analyzed, and they showed expected differences in both internal and external behaviors between neurotypical (46,XY) boys and boys with 49,XXXXY. There were several CpGs in AR and MAOA of boys with 49,XXXXY whose methylation levels were skewed from levels predicted from having one active (Xa) and three inactive (Xi) X chromosomes. Further, methylation levels of multiple CpGs in MAOA showed nominally significant association with externalizing behavior on the CBCL, and the methylation level of one CpG in AR showed nominally significant association with the BRIEF Regulation Index. Conclusions Boys with 49,XXXXY displayed higher levels of CpG methylation at regulatory intronic regions in X-linked genes encoding the androgen receptor (AR) and monoamine oxidase A (MAOA), compared to that in boys with 47,XXY and neurotypical boys. Our pilot study results suggest a link between CpG methylation levels and behavior in boys with 49,XXXXY.

scholarly journals Molecular Characterization of hobo-Mediated Inversions in Drosophila melanogaster

Genetics ◽  
1996 ◽  
Vol 144 (2) ◽  
pp. 647-656
Author(s):  
William B Eggleston ◽  
Nac R Rim ◽  
Johng K Lim
Keyword(s):  
X Chromosome ◽  
Polymerase Chain Reaction Amplification ◽  
Polytene Chromosomes ◽  
Chromosomal Inversions ◽  
Hobo Element ◽  
Reaction Amplification ◽  
Notch Locus ◽  
Polymerase Chain

Abstract The structure of chromosomal inversions mediated by hobo transposable elements in the Uc-1 X chromosome was investigated using cytogenetic and molecular methods. Uc-1 contains a phenotypically silent hobo element inserted in an intron of the Notch locus. Cytological screening identified six independent Notch mutations resulting from chromosomal inversions with one breakpoint at cytological position 3C7, the location of Notch. In situ hybridization to salivary gland polytene chromosomes determined that both ends of each inversion contained hobo and Notch sequences. Southern blot analyses showed that both breakpoints in each inversion had hobo-Notch junction fragments indistinguishable in structure from those present in the Uc-1 X chromosome prior to the rearrangements. Polymerase chain reaction amplification of the 12 hobo-Notch junction fragments in the six inversions, followed by DNA sequence analysis, determined that each was identical to one of the two hobo-Notch junctions present in Uc-1. These results are consistent with a model in which hobo-mediated inversions result from homologous pairing and recombination between a pair of hobo elements in reverse orientation.

scholarly journals Absence of X-chromosome dosage compensation in the primordial germ cells of Drosophila embryos

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ryoma Ota ◽  
Makoto Hayashi ◽  
Shumpei Morita ◽  
Hiroki Miura ◽  
Satoru Kobayashi
Keyword(s):  
X Chromosome ◽  
Germ Cells ◽  
Dosage Compensation ◽  
Sex Chromosome ◽  
Primordial Germ Cells ◽  
Histone H4 ◽  
X Chromosomes ◽  
Essential Components ◽  
Msl Complex ◽  
Male Specific

AbstractDosage compensation is a mechanism that equalizes sex chromosome gene expression between the sexes. In Drosophila, individuals with two X chromosomes (XX) become female, whereas males have one X chromosome (XY). In males, dosage compensation of the X chromosome in the soma is achieved by five proteins and two non-coding RNAs, which assemble into the male-specific lethal (MSL) complex to upregulate X-linked genes twofold. By contrast, it remains unclear whether dosage compensation occurs in the germline. To address this issue, we performed transcriptome analysis of male and female primordial germ cells (PGCs). We found that the expression levels of X-linked genes were approximately twofold higher in female PGCs than in male PGCs. Acetylation of lysine residue 16 on histone H4 (H4K16ac), which is catalyzed by the MSL complex, was undetectable in these cells. In male PGCs, hyperactivation of X-linked genes and H4K16ac were induced by overexpression of the essential components of the MSL complex, which were expressed at very low levels in PGCs. Together, these findings indicate that failure of MSL complex formation results in the absence of X-chromosome dosage compensation in male PGCs.

scholarly journals Escape from X Chromosome Inactivation and the Female Predominance in Autoimmune Diseases

2021 ◽  
Vol 22 (3) ◽  
pp. 1114
Author(s):  
Ali Youness ◽  
Charles-Henry Miquel ◽  
Jean-Charles Guéry
Keyword(s):  
Autoimmune Diseases ◽  
X Chromosome ◽  
Gene Dosage ◽  
X Chromosome Inactivation ◽  
Chromosome Inactivation ◽  
X Chromosomes ◽  
Female Sex Hormones ◽  
Inactive X Chromosome ◽  
Immune Related Genes ◽  
Female Specific

Women represent 80% of people affected by autoimmune diseases. Although, many studies have demonstrated a role for sex hormone receptor signaling, particularly estrogens, in the direct regulation of innate and adaptive components of the immune system, recent data suggest that female sex hormones are not the only cause of the female predisposition to autoimmunity. Besides sex steroid hormones, growing evidence points towards the role of X-linked genetic factors. In female mammals, one of the two X chromosomes is randomly inactivated during embryonic development, resulting in a cellular mosaicism, where about one-half of the cells in a given tissue express either the maternal X chromosome or the paternal one. X chromosome inactivation (XCI) is however not complete and 15 to 23% of genes from the inactive X chromosome (Xi) escape XCI, thereby contributing to the emergence of a female-specific heterogeneous population of cells with bi-allelic expression of some X-linked genes. Although the direct contribution of this genetic mechanism in the female susceptibility to autoimmunity still remains to be established, the cellular mosaicism resulting from XCI escape is likely to create a unique functional plasticity within female immune cells. Here, we review recent findings identifying key immune related genes that escape XCI and the relationship between gene dosage imbalance and functional responsiveness in female cells.

scholarly journals SITE-SPECIFIC INSTABILITY IN DROSOPHILA MELANOGASTER: EVIDENCE FOR TRANSPOSITION OF DESTABILIZING ELEMENT

Genetics ◽  
1982 ◽  
Vol 101 (3-4) ◽  
pp. 461-476
Author(s):  
Todd R Laverty ◽  
J K Lim
Keyword(s):  
Drosophila Melanogaster ◽  
X Chromosome ◽  
Lethal Mutation ◽  
Chromosome Rearrangements ◽  
Chromosome Break ◽  
Secondary Mutation ◽  
X Chromosomes ◽  
Site Specific ◽  
Normal Sequence ◽  
Lethal Mutations

ABSTRACT In this study, we show that at least one lethal mutation at the 3F-4A region of the X chromosome can generate an array of chromosome rearrangements, all with one chromosome break in the 3F-4A region. The mutation at 3F-4A (secondary mutation) was detected in an X chromosome carrying a reverse mutation of an unstable lethal mutation, which was mapped in the 6F1-2 doublet (primary mutation). The primary lethal mutation at 6F1-2 had occurred in an unstable chromosome (Uc) described previously (Lim 1979). Prior to reversion, the 6F1-2 mutation had generated an array of chromosome rearrangements, all having one break in the 6F1-2 doublet (Lim 1979, 1980). In the X chromosomes carrying the 3F-4A secondary lethal mutation the 6F1-2 doublet was normal and stable, as was the 3F-4A region in the X chromosome carrying the primary lethal mutation. The disappearance of the instability having a set of genetic properties at one region (6F1-2) accompanied by its appearance elsewhere in the chromosome (3F-4A) implies that a transposition of the destabilizing element took place. The mutant at 3F-4A and other secondary mutants exhibited all but one (reinversion of an inversion to the normal sequence) of the eight properties of the primary lethal mutations. These observations support the view that a transposable destabilizing element is responsible for the hypermutability observed in the unstable chromosome and its derivaties.

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