scholarly journals CENTROMERIC EFFECT ON THE DEGREE OF NONRANDOM DISJUNCTION IN THE FEMALE DROSOPHILA MELANOGASTER

Genetics ◽  
1977 ◽  
Vol 86 (1) ◽  
pp. 121-132
Author(s):  
Hon Fong Louie Mark ◽  
Stanley Zimmering
Keyword(s):  
Drosophila Melanogaster ◽  
X Chromosome ◽  
Negative Correlation ◽  
Sex Chromosome ◽  
Double Exchange ◽  
Distal Region ◽  
Unexpected Result ◽  
Preferential Segregation ◽  
Single Exchange ◽  
Time Required

ABSTRACT From crosses of females possessing a heteromorphic X-chromosome bivalent, FR1/+, the shorter crossover products were recovered on the average more frequently than the longer reciprocals as predicted by Novitski's (1951) hypothesis of nonrandom disjunction (NRD). The present study stemmed from an unexpected result of these crosses. Evidence for a centromeric effect on NRD was obtained, suggested by a negative correlation between the degree of NRD, c, and the distance between the region of exchange and the centromere as inferred from SET's (single exchange tetrads). Studies on sex chromosome systems other than FR1 confirmed these results. An analogous centromeric effect on preferential segregation had been clearly demonstrated in maize (Kikudome 1958, 1959; Rhoades and Dempsey 1966). However, prior to the present investigation, no such effect of the centromere on NRD in Drosophila had been described, although reanalysis of part of the data of Novitski (1951) and Novitski and Sandler (1956) suggests some evidence of a seriation of increasing c values extending from the most distal region of the chromosome toward the centromere. A suggestion that the effect in Drosophila may be related in some way to the time required for chiasma terminalization, i.e., those terminalizing earlier (distally located crossovers) permitting more random disjunction of the chromatids from the asymmetric dyad and those terminalizing later, progressively less random, is considered and rejected since in general the expected pattern of c values for the various double exchange tetrads (DET's) is inconsistent with that prediction and provides evidence suggesting the possibility of reversals, in part, of c values obtained for SET's.

scholarly journals The Influence of Chromosomal Environment on X-Linked Gene Expression in Drosophila melanogaster

2020 ◽  
Vol 12 (12) ◽  
pp. 2391-2402
Author(s):  
Aleksei Belyi ◽  
Eliza Argyridou ◽  
John Parsch
Keyword(s):  
Gene Expression ◽  
Drosophila Melanogaster ◽  
Binding Site ◽  
X Chromosome ◽  
Dosage Compensation ◽  
Negative Correlation ◽  
Expression Ratio ◽  
Linked Gene ◽  
Somatic Tissues ◽  
Male To Female

Abstract Sex chromosomes often differ from autosomes with respect to their gene expression and regulation. In Drosophila melanogaster, X-linked genes are dosage compensated by having their expression upregulated in the male soma, a process mediated by the X-chromosome-specific binding of the dosage compensation complex (DCC). Previous studies of X-linked gene expression found a negative correlation between a gene’s male-to-female expression ratio and its distance to the nearest DCC binding site in somatic tissues, including head and brain, which suggests that dosage compensation influences sex-biased gene expression. A limitation of the previous studies, however, was that they focused on endogenous X-linked genes and, thus, could not disentangle the effects of chromosomal position from those of gene-specific regulation. To overcome this limitation, we examined the expression of an exogenous reporter gene inserted at many locations spanning the X chromosome. We observed a negative correlation between the male-to-female expression ratio of the reporter gene and its distance to the nearest DCC binding site in somatic tissues, but not in gonads. A reporter gene’s location relative to a DCC binding site had greater influence on its expression than the local regulatory elements of neighboring endogenous genes, suggesting that intra-chromosomal variation in the strength of dosage compensation is a major determinant of sex-biased gene expression. Average levels of sex-biased expression did not differ between head and brain, but there was greater positional effect variation in the brain, which may explain the observed excess of endogenous sex-biased genes located on the X chromosome in this tissue.

Adding the heterochromatic YL arm to an X chromosome reduces reproductive fitnesses in Drosophila melanogaster: implications for the evolution of rDNA, heterochromatin, and reproductive isolation

Genome ◽  
1990 ◽  
Vol 33 (3) ◽  
pp. 340-347 ◽  
Author(s):  
R. Frankham
Keyword(s):  
Drosophila Melanogaster ◽  
Reproductive Isolation ◽  
X Chromosome ◽  
Sex Chromosome ◽  
Reproductive Fitness ◽  
Chromosome Translocation ◽  
Translocation Chromosome ◽  
X Chromosomes ◽  
The Face ◽  
Over Time

For X–Y exchange to be of importance in the coevolution of X and Y rDNA, there must be a mechanism to maintain cytologically normal X chromosomes in the face of continual infusions of X.YL chromosomes produced by X–Y exchanges. Replicated populations were founded with different frequencies of isogenic X and X.YL chromosomes. The X.YL chromosome declined in frequency over time in all lines. Relative fitnesses, estimated from chromosome frequency trajectories, were 0.40, 1.01, and 1.0 for X.YL/X.YL, X.YL/X, and X/X females and 0.75 and 1.0 for X.YL/Y and X/Y males, respectively. The equilibrium frequency for the X.YL chromosome due to the balance between X–Y exchange and selection was predicted to be 4–16 × 10−4. The results strengthen the evidence for the involvement of X–Y exchange in the coevolution of X and Y rDNA arrays. Conditions for the evolution of reproductive isolation by sex-chromosome translocation are much less probable than previously supposed since the X.YL translocation chromosome is at a selective disadvantage to cytologically normal X chromosomes. Additional heterochromatin was not neutral but was only deleterious beyond a threshold, as one dose of the heterochromatic XL arm did not reduce female reproductive fitness, but two doses did.Key words: Drosophila, rRNA, heterochromatin, fitness, speciation.

scholarly journals Chromatin at X-linked repeats that guide dosage compensation in Drosophila melanogaster is modulated by the siRNA pathway

2018 ◽  
Author(s):  
Nikita Deshpande ◽  
Victoria H. Meller
Keyword(s):  
Drosophila Melanogaster ◽  
X Chromosome ◽  
Sex Chromosome ◽  
Gene Dosage ◽  
Ectopic Expression ◽  
Dependent Manner ◽  
Satellite Repeats ◽  
Msl Complex ◽  
Dependent Modification ◽  
Sirna Pathway

AbstractMany heterogametic organisms adjust sex chromosome expression to accommodate differences in gene dosage. This requires selective recruitment of regulatory factors to the modulated chromosome. How these factors are localized to a chromosome with requisite accuracy is poorly understood. Drosophila melanogaster males increase expression from their single X chromosome. Identification of this chromosome involves cooperation between different classes of X-identity elements. The Chromatin Entry Sites (CES) recruit a chromatin-modifying complex that spreads into nearby genes and increases expression. In addition, a family of satellite repeats that is enriched on the X chromosome, the 1.688X repeats, promotes recruitment of the complex to nearby genes. The 1.688X repeats and CES are dissimilar, and appear to operate through different mechanisms. Interestingly, the siRNA pathway and siRNA from a 1.688X repeat also promote X recognition. We postulate that siRNA-dependent modification of 1.688X chromatin contributes to recognition of nearby genes. In accord with this, we found enrichment of the siRNA effector Argonaute2 (Ago2) at some 1.688X repeats.Mutations in several proteins that physically interact with Ago2, including the histone methyltransferase Su(var)3-9, enhance the lethality of males with defective X recognition. Su(var)3-9 deposits H3K9me2 on some 1.688X repeats, and this mark is disrupted upon ectopic expression of 1.688X siRNA. Furthermore, integration of 1.688X DNA on an autosome induces local H3K9me2 deposition, but enhances expression of nearby genes in a siRNA-dependent manner. Our findings are consistent with a model in which siRNA-directed modification of 1.688X chromatin contributes to recognition of the fly X chromosome by the MSL complex.

scholarly journals A genetic analysis of male-predominant pheromones in Drosophila melanogaster.

Genetics ◽  
1988 ◽  
Vol 119 (3) ◽  
pp. 639-646
Author(s):  
D Scott ◽  
R C Richmond
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Analysis ◽  
X Chromosome ◽  
Negative Correlation ◽  
Genetic Basis ◽  
Backcross Progeny ◽  
Significant Negative Correlation ◽  
Chemical Signals ◽  
Incomplete Dominance ◽  
Important Variation

Abstract Chemical signals from males play an important role in stimulating Drosophila melanogaster females to mate, and male-predominant pheromones may influence a female's choice of mates. Male-predominant pheromones also inhibit courtship, thereby functioning as antiaphrodisiacs. Interstrain variation in the ratio of two male-predominant pheromones (7-tricosene and 7-pentacosene) has been reported, but the genetic basis for this potentially important variation has not been examined. In a series of crosses between strains that differ radically in the amounts of 7-tricosene and 7-pentacosene, we have identified both X-linked and autosomal contributions to interstrain variation in the amounts of these compounds. The X-linked loci act as enhancers for production of the compound predominant in the strain from which the X chromosome originated. Autosomal factors for each of the two compounds appear to segregate as high vs. low, with incomplete dominance of high 7-tricosene over low, and low 7-pentacosene over high. A significant negative correlation between the quantities of 7-pentacosene and 7-tricosene in the F2 and backcross progeny, but not in the F1s or parentals, indicates linkage between autosomal loci regulating the expression of each compound. However, the phenotypic distributions of the backcross progeny indicate that additional unlinked loci are also directly involved in the production of these two hydrocarbons.

THE EFFECTS OF URETHANE, SODIUM MONOHYDROGEN ARSENATE AND SELENOCYSTINE ON CROSSING-OVER IN DROSOPHILA MELANOGASTER

1975 ◽  
Vol 17 (1) ◽  
pp. 55-66 ◽  
Author(s):  
Zia U. Ahmed ◽  
G. W. R. Walker
Keyword(s):  
Drosophila Melanogaster ◽  
Double Exchange ◽  
Chemical Treatments ◽  
Repair Enzymes ◽  
Recombination Repair ◽  
Single Exchange ◽  
Natural Recombination ◽  
Pupal Mortality ◽  
Male Specific ◽  
Concentration Curves

The effects of 0–25 mM urethane, 0–50 μM selenocystine and 0–100 μM sodium monohydrogen arsenate on marker-exchange frequencies have been studied along a region of the X chromosome of Drosophila melanogaster marked by y, cv, v and f. Clear and consistent effects seen in concentration curves were usually but not always found significant in analyses of variance. Urethane concentration curves rose to a higher level at 0.5 to 3 mM and dropped to control levels between 10 and 25 mM. It is proposed that this reversibility was due to a competition between two categories of lesions mimicking natural recombination sites, those on unpaired regions of the chromosome competing with those on already paired regions for recombination-repair enzymes. Selenocystine affected exchange frequencies mainly toward the ends of the unmarked region, especially y – cv, negatively from 2 to 10 μM and positively above 10 μM. These effects are interpreted as being mediated by selenocystine control over restriction of synaptic pairing to terminal regions, especially y – cv. Interactions between urethane and selenocystine in two-chemical treatments satisfactorily support the above explanations for both the urethane and selenocystine effects. Sodium monohydrogen arsenate effects, tentatively attributed to the arsenate ion, differed markedly from those of the other chemicals: "arsenate" concentration curves for single-exchange classes tended to be broadly convex and those for double-exchange classes concave, while interactions with urethane tended to be synergistic or neutral except in one exchange class (that for single exchange in y – cv). No satisfactory explanation of the arsenate effects has yet been found. At 25 mM only, urethane caused male-specific, 95% pupal mortality.

INTERACTING EFFECTS OF SODIUM MONOHYDROGENARSENATE AND SELENOCYSTINE ON CROSSING OVER IN DROSOPHILA MELANOGASTER

1969 ◽  
Vol 11 (3) ◽  
pp. 677-688 ◽  
Author(s):  
G. W. R. Walker ◽  
Amelia M. Bradley
Keyword(s):  
Drosophila Melanogaster ◽  
Marked Effect ◽  
Double Exchange ◽  
Crossing Over ◽  
Chromosomal Protein ◽  
General Effect ◽  
Initial Region ◽  
Concentration Region ◽  
Single Exchange ◽  
Concentration Curves

Drosophila melanogaster females of X chromosome genotype y cυ υ f/++++ were reared as larvae on 16-treatment media, representing the various combinations of four concentrations each of sodium monohydrogen arsenate and selenocystine (concentrations were 0, 2, 10 and 50 μM). The fourfold replication of selenocystine curves at four arsenate levels confirmed the existence of a selenocystine effect indicated earlier (Ting and Walker, 1969), as well as the segmental differences in and reversibility of the effect. A marked "sink" in crossing over was found both in total single exchange chromosomes and total double exchange chromosomes at 10 μM selenocystine and peaks in single exchange for segment 1 and for the whole chromosome and for double exchange for segments 1 and 2 at 2 μM were noted. In addition, arsenate was shown to exert a marked effect in the selenocystine-concentration region 0-10 μM; crossover frequencies were quite consistently increased by arsenate treatment at zero selenocystine, and considerable differences were introduced into the initial region (0-2 μM) of selenocystine segmental curves by arsenate treatment, with resultant increases in total single exchange and double exchange curves. In addition, the general effect was noted in arsenate-concentration curves, at 2 and 10 μM As: a drop in double exchange and an increase in single exchanges. Hypotheses are presented relating these effects to possibilities regarding the incorporation of selenocystine and arsenate into chromosomal protein and DNA respectively.

X-4 Translocations and Meiotic Drive in Drosophila melanogaster Males: Role of Sex Chromosome Pairing

Genetics ◽  
1987 ◽  
Vol 116 (3) ◽  
pp. 409-413
Author(s):  
Bruce McKee
Keyword(s):  
Drosophila Melanogaster ◽  
Y Chromosome ◽  
X Chromosome ◽  
Chromosome Pairing ◽  
Sex Chromosome ◽  
Meiotic Drive ◽  
Meiotic Pairing ◽  
Size Dependent ◽  
Chromosome Breakpoint

ABSTRACT Males carrying certain X-4 translocations exhibit strongly skewed sperm recovery ratios. The XP4D half of the translocation disjoins regularly from the Y chromosome and the 4PXD half disjoins regularly from the normal 4. Yet the smaller member of each bivalent is recovered in excess of its pairing partner, apparently due to differential gametic lethality. Chromosome recovery probabilities are multiplicative; the viability of each genotype is the product of the recovery probability of its component chromosomes. Meiotic drive can also be caused by deficiency for X heterochromatin. In(1)sc4Lsc8R males show the same size dependent chromosome recoveries and multiplicative recovery probabilities found in T(1;4)BS males. Meiotic drive in In(1)sc4Lsc8R males has been shown to be due to X-Y pairing failure. Although pairing is regular in the T(X;4) males, the striking phenotypic parallels suggest a common explanation. The experiments described below show that the two phenomena are, in fact, one and the same. X-4 translocations are shown to have the same effect on recovery of independently assorting chromosomes as does In(1)sc4Lsc8R. Addition of pairing sites to the 4PXD half of the translocation eliminates drive. A common explanation—failure of the distal euchromatic portion of the X chromosome to participate in X:Y meiotic pairing—is suggested as the cause for drive. The effect of X chromosome breakpoint on X-4 translocation induced meiotic drive is investigated. It is found that translocations with breakpoints distal to 13C on the salivary map do not cause drive while translocations broken proximal to 13C cause drive. The level of drive is related to the position of the breakpoint—the more proximal the breakpoint the greater the drive.

scholarly journals HETEROCHROMATIC EFFECTS ON THE BEHAVIOR OF REVERSED ACROCENTRIC COMPOUND-X CHROMOSOMES IN DROSOPHILA MELANOGASTER

Genetics ◽  
1979 ◽  
Vol 91 (3) ◽  
pp. 537-551
Author(s):  
L Sandler ◽  
Joseph O'Tousa
Keyword(s):  
Drosophila Melanogaster ◽  
Y Chromosome ◽  
X Chromosome ◽  
Egg Production ◽  
Heterochromatic Region ◽  
Meiotic Behavior ◽  
X Chromosomes ◽  
General Properties ◽  
Single Exchange

ABSTRACT Previous studies of reversed acrocentric compound-X chromosomes suggested peculiar influences of heterochromatin on both the synthesis and meiotic behavior of such compounds. It seemed, with respect to synthesis, that the long arm of the Y chromosome on an X.YL chromosome was necessary in order for the heterochromatic exchange giving rise to reversed acrocentrics to occur, even though YL itself did not participate in the compound-generating event. With respect to behavior, the resulting compounds appeared, presumably as a consequence of their singular generation, to contain an interstitial heterochromatic region that caused the distribution of exchanges between the elements of the compound to be abnormal (many zero and two-exchange tetrads with few, if any, single-exchange tetrads). Removing the interstitial heterochromatin (or, curiously, appending YL as a second arm of the compound) eliminated the recombinational anomalies and resulted in typical tetrad distributions.—We provide evidence that these peculiarities, while presumably real, were likely the consequence of a special X.YL chromosome that was used to synthesize the reversed acrocentrics examined in the early studies and are not general properties of either reversed acrocentric compounds or of interstitial heterochromatin. However, we show that specific heterochromatic regions do, in fact, profoundly influence the behavior of (apparently all) reversed acrocentric compound-X chromosomes. In particular, we demonstrate that specific portions of the Y chromosome and of the basal X-chromosome heterochromatin, when present as homologs for reversed acrocentric compounds, markedly and coordinately increase bath the frequency of exchange between the elements of the compound and the fertility (egg production) of compound-bearing females. It is, we suppose, some aspect of this heterochromatic effect, produced by the% special X.YL chromosome, that caused the earlier-analyzed compounds to exhibit the observed anomalies.

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 Deficit of Mitonuclear Genes on the Human X Chromosome Predates Sex Chromosome Formation

2015 ◽  
Vol 7 (2) ◽  
pp. 636-641 ◽  
Author(s):  
Rebecca Dean ◽  
Fabian Zimmer ◽  
Judith E. Mank
Keyword(s):  
X Chromosome ◽  
Sex Chromosome ◽  
Chromosome Formation
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