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 Puffing activity in Drosophila melanogaster Meig. political chromosomes after exposure to microwave radiation

2018 ◽  
Vol 23 ◽  
pp. 393-398
Author(s):  
M. N. Sheyka ◽  
V. Yu. Strashnyuk
Keyword(s):  
Drosophila Melanogaster ◽  
Salivary Glands ◽  
Power Density ◽  
Microwave Radiation ◽  
X Chromosome ◽  
Polytene Chromosomes ◽  
Early Embryogenesis ◽  
Wild Type ◽  
Ocular Micrometer ◽  
Outbred Strain

Aim. The aim of the work was to study the effect of microwave radiation of varying intensity on the polytene chromosomes puffing activity in larvae salivary glands of Drosophila melanogaster. Methods. The wild type outbred strain Oregon-R was used as the material. Microwave radiation with a frequency of 36.64 GHz and a power density of 0.1 and 1 W / m2 was used. Exposure to microwaves was applied in early embryogenesis after 3-hour oviposition. Exposure time was 30 sec. The puff sizes were studied on the squashed preparations of larvae salivary glands stained with acetoorcein. Dimensions of four puffs were investigated^ 2B5-6 (X chromosome); 62E, 71CE and 72CD (chromosome 3L). The measurements were carried out using an ocular-micrometer. Results. There were no significant changes in the size of the puffs in any of the four loci studied, regardless of the applied power density. Conclusions. Microwave radiation in early embryogenesis at a frequency of 36.64 GHz, a power density of 0.1 and 1 W/m2, and an exposure of 30 sec does not have a significant effect on the puff sizes in the Drosophila polytene chromosomes. Keywords: Drosophila melanogaster Meig., giant chromosomes, puff sizes, non-ionizing radiation.

scholarly journals Chromosomal basis of dosage compensation in drosophila: IX. cellular autonomy of the faster replication of the x chromosome in haplo-x cells of drosophila melanogaster and synchronous initiation

1977 ◽  
Vol 74 (1) ◽  
pp. 168-180 ◽  
Author(s):  
RN Chatterjee ◽  
AS Mukherjee
Keyword(s):  
Drosophila Melanogaster ◽  
Salivary Glands ◽  
X Chromosome ◽  
Initial Phase ◽  
X Chromosomes ◽  
Initiation Of Replication ◽  
A Genome ◽  
The Mean ◽  
Early Replication ◽  
X Cells

[(3)H]Thymidine labeling patterns have been examined in gynandric mosaic salivary glands of drosophila melanogaster. The Ring-X stock, R(1) w(ve)/In(1)dl 49, l (1) J1 y w lz(s), was used for this purpose. 365 labeled XX2A and 40 labeled XO2A nuclei were obtained from a total of 624 nuclei in nine pairs of mosaic salivary glands. It was observed that in all but those nuclei which had DD, 1C, and 2C patterns, the X chromosome of the XO2A nuclei always had fewer sites labeled than the X chromosomes of the XX2A nuclei, for a given pattern of the autosomes in either sex. Such asynchronous labeling of the X chromosome in the XO2A (male) nuclei was observed regardless of the proportion of the XO2A cells (2.0-73.7 percent), in the mosaic glands. Moreover, while the frequency of [(3)H]thymidine labeling for all of the 39 replicating units except the two late replicating sites (3C and 11A) in the X chromosome of the XO2A nuclei, was consistently lower than in the X chromosome of the XX2A nuclei, the mean number of grains on the X chromosome was relatively (to autosomes) similar in both XX2A and XO2A cells. The results, therefore, suggest that, as in XY2A larval glands, the X chromosome in the XO2A cells also completes the replication earlier than autosomes and that the XO2A nuclei show cellular autonomy with respect to the early replication of the X chromosome, like its counterpart, RNA transcription. Absence of the asynchrony during the initial phase (DD-2C) further completes the replication earlier but that the rate of replication of its DNA is possibly faster, and (b) that there might be a common regulation with respect to the initiation of replication of different chromosomes in a genome.

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 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.

scholarly journals Hybrid dysgenesis-induced quantitative variation on the X chromosome of Drosophila melanogaster.

Genetics ◽  
1990 ◽  
Vol 124 (3) ◽  
pp. 627-636
Author(s):  
C Q Lai ◽  
T F Mackay
Keyword(s):  
Drosophila Melanogaster ◽  
X Chromosome ◽  
Quantitative Traits ◽  
Natural Populations ◽  
Quantitative Variation ◽  
Hybrid Dysgenesis ◽  
X Chromosomes ◽  
Bristle Number ◽  
Seven Generations ◽  
Polygenic Variation

Abstract To determine the ability of the P-M hybrid dysgenesis system of Drosophila melanogaster to generate mutations affecting quantitative traits, X chromosome lines were constructed in which replicates of isogenic M and P strain X chromosomes were exposed to a dysgenic cross, a nondysgenic cross, or a control cross, and recovered in common autosomal backgrounds. Mutational heritabilities of abdominal and sternopleural bristle score were in general exceptionally high-of the same magnitude as heritabilities of these traits in natural populations. P strain chromosomes were eight times more mutable than M strain chromosomes, and dysgenic crosses three times more effective than nondysgenic crosses in inducing polygenic variation. However, mutational heritabilities of the bristle traits were appreciable for P strain chromosomes passed through one nondysgenic cross, and for M strain chromosomes backcrossed for seven generations to inbred P strain females, a result consistent with previous observations on mutations affecting quantitative traits arising from nondysgenic crosses. The new variation resulting from one generation of mutagenesis was caused by a few lines with large effects on bristle score, and all mutations reduced bristle number.

scholarly journals Sex and death: from cell fate specification to dynamic control of X-chromosome structure and gene expression

2018 ◽  
Vol 29 (22) ◽  
pp. 2616-2621 ◽  
Author(s):  
Barbara J. Meyer
Keyword(s):  
Gene Expression ◽  
Cell Fate ◽  
X Chromosome ◽  
Chromosome Structure ◽  
Dynamic Control ◽  
Three Dimensional ◽  
X Chromosomes ◽  
Meiotic Chromosomes ◽  
The Difference ◽  
Developmental Decision

Determining sex is a binary developmental decision that most metazoans must make. Like many organisms, Caenorhabditis elegans specifies sex (XO male or XX hermaphrodite) by tallying X-chromosome number. We dissected this precise counting mechanism to determine how tiny differences in concentrations of signals are translated into dramatically different developmental fates. Determining sex by counting chromosomes solved one problem but created another—an imbalance in X gene products. We found that nematodes compensate for the difference in X-chromosome dose between sexes by reducing transcription from both hermaphrodite X chromosomes. In a surprising feat of evolution, X-chromosome regulation is functionally related to a structural problem of all mitotic and meiotic chromosomes: achieving ordered compaction of chromosomes before segregation. We showed the dosage compensation complex is a condensin complex that imposes a specific three-­dimensional architecture onto hermaphrodite X chromosomes. It also triggers enrichment of histone modification H4K20me1. We discovered the machinery and mechanism underlying H4K20me1 enrichment and demonstrated its pivotal role in regulating higher-order X-chromosome structure and gene expression.

Spontaneous formation of compound X chromosomes in Drosophila melanogaster.

Genetics ◽  
1988 ◽  
Vol 119 (1) ◽  
pp. 95-103
Author(s):  
R J Morrison ◽  
J D Raymond ◽  
J R Zunt ◽  
J K Lim ◽  
M J Simmons
Keyword(s):  
Drosophila Melanogaster ◽  
X Chromosome ◽  
The Other ◽  
X Chromosomes ◽  
Multiple Factors ◽  
Spontaneous Formation ◽  
Chromosome Attachment ◽  
Recombination Experiments ◽  
Attachment Process

Abstract Males carrying different X chromosomes were tested for the ability to produce daughters with attached-X chromosomes. This ability is characteristic of males carrying an X chromosome derived from 59b-z, a multiply marked X chromosome, and is especially pronounced in males carrying the unstable 59b-z chromosomes Uc and Uc-lr. Recombination experiments with one of the Uc-lr chromosomes showed that the formation of compound chromosomes depends on two widely separated segments. One of these is proximal to the forked locus and is probably proximal to the carnation locus. This segment may contain the actual site of chromosome attachment. The other essential segment lies between the crossveinless and vermilion loci and may contain multiple factors that influence the attachment process.

scholarly journals MEIOTIC BEHAVIOR OF COMPOUND AUTOSOMES IN FEMALES OF DROSOPHILA MELANOGASTER: INTERCHROMOSOMAL EFFECTS AND THE SOURCE OF SPONTANEOUS NONSEGREGATION

Genetics ◽  
1980 ◽  
Vol 96 (2) ◽  
pp. 455-470
Author(s):  
Hideh Harger ◽  
David G Holm
Keyword(s):  
Drosophila Melanogaster ◽  
X Chromosome ◽  
Inverse Correlation ◽  
Proximal Region ◽  
Crossing Over ◽  
X Chromosomes ◽  
Repulsion Phase ◽  
Base Level ◽  
Exchange Processes ◽  
Spontaneous Frequency

ABSTRACT In females of Drosophila melanogaster, compound autosomes enter the repulsion phase of meiosis uncommitted to a particular segregation pattern because their centromeres are not restricted to a bivalent pairing complex as a consequence of crossing over. Their distribution at anaphase, therefore, is determined by some meiotic property other than exchange pairing, a property that for many years has been associated with the concept of nonhomologous pairing. In the absence of heterologous rearrangements or a free Y chromosome, C(3L) and C(3R) are usually recovered in separate gametes, that is as products of meiotic segregation. Nevertheless, there is a regular, albeit infrequent, recovery of reciprocal meiotic products (the nonsegregational products) that are disomic and nullosomic for compound thirds. The frequency of these exceptions, which is normally between 0.5 and 5.0%, differs for the various strains examined, but remains constant for any given strain. Since previous studies have not uncovered a cause for this base level of nonsegregation, it has been referred to as the spontaneous frequency. In this study, crosses between males and females whose X chromosomes, as well as compound autosomes, are differentially marked reveal a highly significant positive correlation between the frequency of compound-autosome nonsegregation and the frequency of X-chromosome nondisjunction. However, an inverse correlation is found when the frequency of nondisjunction is related to the frequency of crossing over in the proximal region of the X chromosome. These findings have been examined with reference to the distributive pairing and the chromocentral models and interpreted as demonstrating (1) that nonsegregational meiotic events arise primarily as a result of nonhomologous interactions, (2) that forces responsible for the segregation of nonhomologous chromosomes are properties of the chromocentral region, and (3) that these forces come into expression after the exchange processes are complete.

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.

Three-dimensional organization of telomeres in nuclei of Drosophila melanogaster salivary glands

2008 ◽  
Vol 2 (4) ◽  
pp. 376-380
Author(s):  
L. P. Zakharenko ◽  
M. P. Perepelkina ◽  
S. Mai
Keyword(s):  
Drosophila Melanogaster ◽  
Salivary Glands ◽  
Three Dimensional
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