Journal articles on the topic 'X and Y chromosomes'
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1
McAllister, Bryant F. "Sequence Differentiation Associated With an Inversion on the Neo-X Chromosome of Drosophila americana." Genetics 165, no. 3 (November 1, 2003): 1317–28. http://dx.doi.org/10.1093/genetics/165.3.1317.
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Abstract Sex chromosomes originate from pairs of autosomes that acquire controlling genes in the sex-determining cascade. Universal mechanisms apparently influence the evolution of sex chromosomes, because this chromosomal pair is characteristically heteromorphic in a broad range of organisms. To examine the pattern of initial differentiation between sex chromosomes, sequence analyses were performed on a pair of newly formed sex chromosomes in Drosophila americana. This species has neo-sex chromosomes as a result of a centromeric fusion between the X chromosome and an autosome. Sequences were analyzed from the Alcohol dehydrogenase (Adh), big brain (bib), and timeless (tim) gene regions, which represent separate positions along this pair of neo-sex chromosomes. In the northwestern range of the species, the bib and Adh regions exhibit significant sequence differentiation for neo-X chromosomes relative to neo-Y chromosomes from the same geographic region and other chromosomal populations of D. americana. Furthermore, a nucleotide site defining a common haplotype in bib is shown to be associated with a paracentric inversion [In(4)ab] on the neo-X chromosome, and this inversion suppresses recombination between neo-X and neo-Y chromosomes. These observations are consistent with the inversion acting as a recombination modifier that suppresses exchange between these neo-sex chromosomes, as predicted by models of sex chromosome evolution.
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Gillings, M. R., R. Frankham, J. Speirs, and M. Whalley. "X-Y Exchange and the Coevolution of the X and Y rDNA Arrays in Drosophila melanogaster." Genetics 116, no. 2 (June 1, 1987): 241–51. http://dx.doi.org/10.1093/genetics/116.2.241.
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ABSTRACT The nucleolus organizers on the X and Y chromosomes of Drosophila melanogaster are the sites of 200-250 tandemly repeated genes for ribosomal RNA. As there is no meiotic crossing over in male Drosophila, the X and Y chromosomal rDNA arrays should be evolutionarily independent, and therefore divergent. The rRNAs produced by X and Y are, however, very similar, if not identical. Molecular, genetic and cytological analyses of a series of X chromosome rDNA deletions (bb alleles) showed that they arose by unequal exchange through the nucleolus organizers of the X and Y chromosomes. Three separate exchange events generated compound X·YL chromosomes carrying mainly Y-specific rDNA. This led to the hypothesis that X-Y exchange is responsible for the coevolution of X and Y chromosomal rDNA. We have tested and confirmed several of the predictions of this hypothesis: First, X·YL chromosomes must be found in wild populations. We have found such a chromosome. Second, the X·YL chromosome must lose the YL arm, and/or be at a selective disadvantage to normal X+ chromosomes, to retain the normal morphology of the X chromosome. Six of seventeen sublines founded from homozygous X·YLbb stocks have become fixed for chromosomes with spontaneous loss of part or all of the appended YL. Third, rDNA variants on the X chromosome are expected to be clustered within the X+ nucleolus organizer, recently donated ("Y") forms being proximal, and X-specific forms distal. We present evidence for clustering of rRNA genes containing Type 1 insertions. Consequently, X-Y exchange is probably responsible for the coevolution of X and Y rDNA arrays.
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Uno, Yoshinobu, Chizuko Nishida, Chiyo Takagi, Takeshi Igawa, Naoto Ueno, Masayuki Sumida, and Yoichi Matsuda. "Extraordinary Diversity in the Origins of Sex Chromosomes in Anurans Inferred from Comparative Gene Mapping." Cytogenetic and Genome Research 145, no. 3-4 (2015): 218–29. http://dx.doi.org/10.1159/000431211.
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Sex determination in frogs (anurans) is genetic and includes both male and female heterogamety. However, the origins of the sex chromosomes and their differentiation processes are poorly known. To investigate diversity in the origins of anuran sex chromosomes, we compared the chromosomal locations of sex-linked genes in 4 species: the African clawed frog (Xenopus laevis), the Western clawed frog (Silurana/X. tropicalis), the Japanese bell-ring frog (Buergeria buergeri), and the Japanese wrinkled frog (Rana rugosa). Comparative mapping data revealed that the sex chromosomes of X. laevis, X. tropicalis and R. rugosa are different chromosome pairs; however, the sex chromosomes of X. tropicalis and B. buergeri are homologous, although this may represent distinct evolutionary origins. We also examined the status of sex chromosomal differentiation in B. buergeri, which possesses heteromorphic ZW sex chromosomes, using comparative genomic hybridization and chromosome painting with DNA probes from the microdissected W chromosome. At least 3 rearrangement events have occurred in the proto-W chromosome: deletion of the nucleolus organizer region and a paracentric inversion followed by amplification of non-W-specific repetitive sequences.
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Röpke, Albrecht, and Frank Tüttelmann. "MECHANISMS IN ENDOCRINOLOGY: Aberrations of the X chromosome as cause of male infertility." European Journal of Endocrinology 177, no. 5 (November 2017): R249—R259. http://dx.doi.org/10.1530/eje-17-0246.
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Male infertility is most commonly caused by spermatogenetic failure, clinically noted as oligo- or a-zoospermia. Today, in approximately 20% of azoospermic patients, a causal genetic defect can be identified. The most frequent genetic causes of azoospermia (or severe oligozoospermia) are Klinefelter syndrome (47,XXY), structural chromosomal abnormalities and Y-chromosomal microdeletions. Consistent with Ohno’s law, the human X chromosome is the most stable of all the chromosomes, but contrary to Ohno’s law, the X chromosome is loaded with regions of acquired, rapidly evolving genes, which are of special interest because they are predominantly expressed in the testis. Therefore, it is not surprising that the X chromosome, considered as the female counterpart of the male-associated Y chromosome, may actually play an essential role in male infertility and sperm production. This is supported by the recent description of a significantly increased copy number variation (CNV) burden on both sex chromosomes in infertile men and point mutations in X-chromosomal genes responsible for male infertility. Thus, the X chromosome seems to be frequently affected in infertile male patients. Four principal X-chromosomal aberrations have been identified so far: (1) aneuploidy of the X chromosome as found in Klinefelter syndrome (47,XXY or mosaicism for additional X chromosomes). (2) Translocations involving the X chromosome, e.g. nonsyndromic 46,XX testicular disorders of sex development (XX-male syndrome) or X-autosome translocations. (3) CNVs affecting the X chromosome. (4) Point mutations disrupting X-chromosomal genes. All these are reviewed herein and assessed concerning their importance for the clinical routine diagnostic workup of the infertile male as well as their potential to shape research on spermatogenic failure in the next years.
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Willhoeft, Ute, Jutta Mueller-Navia, and Gerald Franz. "Analysis of the sex chromosomes of the Mediterranean fruit fly by microdissected DNA probes." Genome 41, no. 1 (February 1, 1998): 74–78. http://dx.doi.org/10.1139/g97-102.
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In the Mediterranean fruit fly, Ceratitis capitata, the sex-determining region maps to the long arm of the Y chromosome. DNA from this region of the Y chromosome and, for comparison, from the tip of the long arm of the X chromosome, was isolated by microdissection and amplified by degenerate oligonucleotide primer PCR (DOP-PCR). FISH of the Y-chromosomal microdissection products medY1-medY5 to mitotic chromosomes revealed hybridization signals on most of the long arm of the Y chromosome, including the male-determining region, and on the long arm of the X chromosome, as well as weaker signals on the autosomes, some of which were located in the heterochromatin next to the centromeres. The X-chromosomal microdissected probe medX1 revealed strong signals on the sex chromosomes and randomly distributed signals on the autosomes. Chromosomal in situ suppression hybridization indicates that the Y chromosome contains considerable amounts of Y-enriched and Y-specific sequences and that X-enriched sequences are present on the long arm of the X chromosome. The microdissected probes medY1, medY2, and medX1 hybridize to the sex chromosomes of two closely related species,Ceratitis rosa and Trirhithrum coffeae.
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Mahesh, G., N. B. Ramachandra, and H. A. Ranganath. "Autoradiographic study of transcription and dosage compensation in the sex and neo-sex chromosome of Drosophila nasuta nasuta and Drosophila nasuta albomicans." Genome 44, no. 1 (February 1, 2001): 71–78. http://dx.doi.org/10.1139/g00-100.
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Cellular autoradiography is used to study the transcription patterns of the polytene X chromosomes in Drosophila nasuta nasuta and D. n. albomicans. D. n. nasuta, with 2n = 8, includes a pair of complete heteromorphic sex chromosomes, whereas D. n. albomicans, with 2n = 6, has a pair of metacentric neo-sex chromosomes representing incomplete heteromorphic sex chromosomes. The neo-X chromosome has two euchromatic arms, one representing the ancestral X while the other represents the ancestral autosome 3 chromosomes. The metacentric neo-Y chromosome has one arm with a complete heterochromatic ancestral Y and the other arm with a euchromatic ancestral autosome 3. The transcription study has revealed that the X chromosome in D. n. nasuta is hyperactive, suggesting complete dosage compensation, while in the neo-X chromosome of D. n. albomicans the ancestral X chromosome is hyperactive and the ancestral autosome 3, which is part of the neo-sex chromosome, is similar to any other autosomes. This finding shows dosage compensation on one arm (XLx/) of the neo-X chromosome, while the other arm (XR3/YR3) is not dosage compensated and has yet to acquire the dosage compensatory mechanism.Key words: Drosophila, chromosomal races, neo-sex chromosome, transcription and dosage compensation.
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England, P. R., H. W. Stokes, and R. Frankham. "Clustering of rDNA containing type 1 insertion sequence in the distal nucleolus organiser of Drosophila melanogaster: implications for the evolution of X and Y rDNA arrays." Genetical Research 51, no. 3 (June 1988): 209–15. http://dx.doi.org/10.1017/s0016672300024307.
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SummaryThe ribosomal RNAs produced by the multigene families on the X and Y chromosomes of Drosophila melanogaster are very similar despite the apparent evolutionary isolation of the X and Y chromosomal rDNA. X–Y exchange through the rDNA is one mechanism that may promote co-evolution of the two gene clusters by transferring Y rDNA copies to the X chromosome. This hypothesis predicts that the proximal rDNA of X chromosomes will be Y-like. Consequently, rDNA variants found only on the X chromosome (such as those interrupted by type 1 insertions) should be significantly clustered in the distal X nucleolus organizer. Proximal and distal portions of the X chromosome nucleolus organizer were separated by recombination between the inverted chromosomes In(1)scv2 (breakpoint in the centre of the rDNA) and In(1)sc4Lsc8R (no rDNA). Molecular analyses of the resulting stocks demonstrated that rRNA genes containing type 1 insertions were predominantly located on the chromosome carrying the distal portion of the X rDNA, thus confirming a prediction of the X–Y exchange hypothesis for the co-evolution of X and Y chromosomal rDNA. Distal clustering is not predicted by the alternative hypotheses of selection or gene conversion.
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Manicardi, G. C., D. C. Gautam, D. Bizzaro, E. Guicciardi, A. M. Bonvicini Pagliai, and U. Bianchi. "Chromosome banding in aphids: G, C, AluI, and HaeIII banding patterns in Megoura viciae (Homoptera, Aphididae)." Genome 34, no. 4 (August 1, 1991): 661–65. http://dx.doi.org/10.1139/g91-101.
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The holocentric mitotic chromosomes of Megoura viciae, a species that has been little studied cytogenetically to date, have been characterized by applying G, C, AluI, and HaeIII banding techniques. C bands have shown the best defined patterns, particularly on the X chromosome. This chromosome, on the other hand, behaved as the most reactive to the various treatments. Uncondensed, prometaphase X chromosomes showed a number of heterochromatic bands, interspersed among the euchromatin, which fused together during metaphase condensation. AluI and HaeIII treatments also produced reproducible banding patterns. These data permit an accurate identification of the X chromosome as well as of the autosomal pairs 1 and 2, and facilitate the construction of nonambiguous karyotypes. They will also stimulate studies on the organization of chromatin in holocentric, holokinetic chromosomes. Finally they could also promote research on chromosomal rearrangements that have occurred during the course of speciation and evolution of aphids, since these kinds of events may be significantly affected by the condition of chromosomal holocentrism.Key words: aphids, holocentric chromosomes, chromosome banding, heterochromatin.
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McAllister, Bryant F., and Brian Charlesworth. "Reduced Sequence Variability on the NeoY Chromosome of Drosophila americana americana." Genetics 153, no. 1 (September 1, 1999): 221–33. http://dx.doi.org/10.1093/genetics/153.1.221.
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Abstract Sex chromosomes are generally morphologically and functionally distinct, but the evolutionary forces that cause this differentiation are poorly understood. Drosophila americana americana was used in this study to examine one aspect of sex chromosome evolution, the degeneration of nonrecombining Y chromosomes. The primary X chromosome of D. a. americana is fused with a chromosomal element that was ancestrally an autosome, causing this homologous chromosomal pair to segregate with the sex chromosomes. Sequence variation at the Alcohol Dehydrogenase (Adh) gene was used to determine the pattern of nucleotide variation on the neo-sex chromosomes in natural populations. Sequences of Adh were obtained for neo-X and neo-Y chromosomes of D. a. americana, and for Adh of D. a. texana, in which it is autosomal. No significant sequence differentiation is present between the neo-X and neo-Y chromosomes of D. a. americana or the autosomes of D. a. texana. There is a significantly lower level of sequence diversity on the neo-Y chromosome relative to the neo-X in D. a. americana. This reduction in variability on the neo-Y does not appear to have resulted from a selective sweep. Coalescent simulations of the evolutionary transition of an autosome into a Y chromosome indicate there may be a low level of recombination between the neo-X and neo-Y alleles of Adh and that the effective population size of this chromosome may have been reduced below the expected value of 25% of the autosomal effective size, possibly because of the effects of background selection or sexual selection.
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Panova, A. V., E. D. Nekrasov, M. A. Lagarkova, S. L. Kiselev, and A. N. Bogomazova. "Late Replication of the Inactive X Chromosome Is Independent of the Compactness of Chromosome Territory in Human Pluripotent Stem Cells." Acta Naturae 5, no. 2 (June 15, 2013): 54–61. http://dx.doi.org/10.32607/20758251-2013-5-2-54-61.
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Dosage compensation of the X chromosomes in mammals is performed via the formation of facultative heterochromatin on extra X chromosomes in female somatic cells. Facultative heterochromatin of the inactivated X (Xi), as well as constitutive heterochromatin, replicates late during the S-phase. It is generally accepted that Xi is always more compact in the interphase nucleus. The dense chromosomal folding has been proposed to define the late replication of Xi. In contrast to mouse pluripotent stem cells (PSCs), the status of X chromosome inactivation in human PSCs may vary significantly. Fluorescence in situ hybridization with a whole X-chromosome-specific DNA probe revealed that late-replicating Xi may occupy either compact or dispersed territory in human PSCs. Thus, the late replication of the Xi does not depend on the compactness of chromosome territory in human PSCs. However, the Xi reactivation and the synchronization in the replication timing of X chromosomes upon reprogramming are necessarily accompanied by the expansion of X chromosome territory.
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Scutt, Charles P., Yasuko Kamisugi, Philip M. Gilmartin, and Fukumi Sakai. "Laser isolation of plant sex chromosomes: studies on the DNA composition of the X and Y sex chromosomes of Silene latifolia." Genome 40, no. 5 (October 1, 1997): 705–15. http://dx.doi.org/10.1139/g97-793.
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X and Y sex chromosomes from the dioecious plant Silene latifolia (white campion) were isolated from mitotic metaphase chromosome preparations on polyester membranes. Autosomes were ablated using an argon ion laser microbeam and isolated sex chromosomes were then recovered on excised fragments of polyester membrane. Sex chromosome associated DNA sequences were amplified using the degenerate oligonucleotide primed polymerase chain reaction (DOP–PCR) and pools of DOP–PCR products were used to investigate the genomic organization of the S. latifolia sex chromosomes. The chromosomal locations of cloned sex chromosome repeat sequences were analysed by fluorescence in situ hybridization and data complementary to laser ablation studies were obtained by genomic in situ hybridization. In combination, these studies demonstrate that the X and Y sex chromosomes of S. latifolia are of very similar DNA composition and also that they share a significant repetitive DNA content with the autosomes. The evolution of sex chromosomes in Silene is discussed and compared with that in another dioecious species, Rumex acetosa.Key words: FISH, GISH, laser-microdissection, sex chromosome, Silene latifolia.
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Cattanach, Bruce M., and Colin V. Beechey. "Autosomal and X-chromosome imprinting." Development 108, Supplement (April 1, 1990): 63–72. http://dx.doi.org/10.1242/dev.108.supplement.63.
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Mouse genetic studies using Robertsonian and reciprocal translations have shown that certain autosomal regions of loci are subject to a parental germ line imprint, which renders maternal and paternal copies functionally inequivalent in the embryo or later stages of development. Duplication of maternal or paternal copies with corresponding paternal/maternal deficiencies in chromosomally balanced zygotes causes various effects. These range from early embryonic lethalities through to mid-fetal and neonatal lethalities, and in some instances viable young with phenotypic effects are obtained. Eight to nine chromosomal regions that give such imprinting effects have been identified. Six to seven of these regions are located in only three chromosomes (2, 7 and 17). The two other regions are located in chromosomes 6 and 11. Maternal and paternal disomies for each of four other chromosomes (1, 5, 9 and 14) have been recovered with different frequencies, but the possibility that this may be due to imprinting has yet to be supported by follow-up studies on regions of the chromosomes concerned. No clear evidence of genetic-background modifications of the imprinting process have been observed in these mouse genetic experiments. The mammalian X chromosome is also subject to imprinting, as demonstrated by the non-random, paternal X-inactivation in female mouse extra-embryonic tissues and in the somatic cells of marsupial females. There is also the opposite bias towards inactivation of the maternal X in the somatic cells of female mice. On the basis that both X-chromosome inactivation and autosomal chromosome imprinting may be concerned with gene regulation, it is suggested that evidence from X-chromosome inactivation studies may help to elucidate factors underlying the imprinting of autosomes. The relevant aspects of X-inactivation are summarized.
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Arnold, Arthur P., Karen Reue, Mansoureh Eghbali, Eric Vilain, Xuqi Chen, Negar Ghahramani, Yuichiro Itoh, et al. "The importance of having two X chromosomes." Philosophical Transactions of the Royal Society B: Biological Sciences 371, no. 1688 (February 19, 2016): 20150113. http://dx.doi.org/10.1098/rstb.2015.0113.
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Historically, it was thought that the number of X chromosomes plays little role in causing sex differences in traits. Recently, selected mouse models have been used increasingly to compare mice with the same type of gonad but with one versus two copies of the X chromosome. Study of these models demonstrates that mice with one X chromosome can be strikingly different from those with two X chromosomes, when the differences are not attributable to confounding group differences in gonadal hormones. The number of X chromosomes affects adiposity and metabolic disease, cardiovascular ischaemia/reperfusion injury and behaviour. The effects of X chromosome number are likely the result of inherent differences in expression of X genes that escape inactivation, and are therefore expressed from both X chromosomes in XX mice, resulting in a higher level of expression when two X chromosomes are present. The effects of X chromosome number contribute to sex differences in disease phenotypes, and may explain some features of X chromosome aneuploidies such as in Turner and Klinefelter syndromes.
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Jesionek, Wojciech, Markéta Bodláková, Zdeněk Kubát, Radim Čegan, Boris Vyskot, Jan Vrána, Jan Šafář, Janka Puterova, and Roman Hobza. "Fundamentally different repetitive element composition of sex chromosomes in Rumex acetosa." Annals of Botany 127, no. 1 (September 9, 2020): 33–47. http://dx.doi.org/10.1093/aob/mcaa160.
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Abstract Background and Aims Dioecious species with well-established sex chromosomes are rare in the plant kingdom. Most sex chromosomes increase in size but no comprehensive analysis of the kind of sequences that drive this expansion has been presented. Here we analyse sex chromosome structure in common sorrel (Rumex acetosa), a dioecious plant with XY1Y2 sex determination, and we provide the first chromosome-specific repeatome analysis for a plant species possessing sex chromosomes. Methods We flow-sorted and separately sequenced sex chromosomes and autosomes in R. acetosa using the two-dimensional fluorescence in situ hybridization in suspension (FISHIS) method and Illumina sequencing. We identified and quantified individual repeats using RepeatExplorer, Tandem Repeat Finder and the Tandem Repeats Analysis Program. We employed fluorescence in situ hybridization (FISH) to analyse the chromosomal localization of satellites and transposons. Key Results We identified a number of novel satellites, which have, in a fashion similar to previously known satellites, significantly expanded on the Y chromosome but not as much on the X or on autosomes. Additionally, the size increase of Y chromosomes is caused by non-long terminal repeat (LTR) and LTR retrotransposons, while only the latter contribute to the enlargement of the X chromosome. However, the X chromosome is populated by different LTR retrotransposon lineages than those on Y chromosomes. Conclusions The X and Y chromosomes have significantly diverged in terms of repeat composition. The lack of recombination probably contributed to the expansion of diverse satellites and microsatellites and faster fixation of newly inserted transposable elements (TEs) on the Y chromosomes. In addition, the X and Y chromosomes, despite similar total counts of TEs, differ significantly in the representation of individual TE lineages, which indicates that transposons proliferate preferentially in either the paternal or the maternal lineage.
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Morrison, R. J., J. D. Raymond, J. R. Zunt, J. K. Lim, and M. J. Simmons. "Spontaneous formation of compound X chromosomes in Drosophila melanogaster." Genetics 119, no. 1 (May 1, 1988): 95–103. http://dx.doi.org/10.1093/genetics/119.1.95.
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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.
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Rovatsos, Michail T., Juan A. Marchal, Ismael Romero-Fernández, Maria Arroyo, Eva B. Athanasopoulou, and Antonio Sánchez. "Extensive Sex Chromosome Polymorphism of Microtus thomasi/Microtus atticus Species Complex Associated with Cryptic Chromosomal Rearrangements and Independent Accumulation of Heterochromatin." Cytogenetic and Genome Research 151, no. 4 (2017): 198–207. http://dx.doi.org/10.1159/000477114.
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The sibling species Microtus thomasi and M. atticus represent probably the highest karyotypic diversity within the genus Microtus and are an interesting model for chromosomal evolution studies. In addition to variation in autosomes, they show a high intraspecific variation in the size and morphology of both sex chromosomes. We analyzed individuals with different sex chromosome constitutions using 3 painting probes, 2 from Y chromosome variants and 1 from the small arm of the submetacentric X chromosome. Our comparative painting approach uncovered 12 variants of Y and 14 variants of X chromosomes, which demonstrates that the polymorphism of sex chromosomes is substantially larger than previously reported. We suggest that 2 main processes are responsible for this sex chromosome polymorphism: change of morphology from acrocentric to submetacentric or metacentric chromosomes and increase in size due to accumulation of repetitive DNA sequences, generating heterochromatic blocks. Strong genetic drift in small and fragmented populations of these 2 species could be related to the origin and maintenance of the large polymorphism of sex chromosomes. We proposed that a similar polymorphism variation combined with random drift fixing the biggest sex chromosomes could have occurred in the origin of some of the actual Microtus species with giant sex chromosomes.
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Gonzalez de la Rosa, Pablo Manuel, Marian Thomson, Urmi Trivedi, Alan Tracey, Sophie Tandonnet, and Mark Blaxter. "A telomere-to-telomere assembly ofOscheius tipulaeand the evolution of rhabditid nematode chromosomes." G3 Genes|Genomes|Genetics 11, no. 1 (December 8, 2020): 1–17. http://dx.doi.org/10.1093/g3journal/jkaa020.
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AbstractEukaryotic chromosomes have phylogenetic persistence. In many taxa, each chromosome has a single functional centromere with essential roles in spindle attachment and segregation. Fusion and fission can generate chromosomes with no or multiple centromeres, leading to genome instability. Groups with holocentric chromosomes (where centromeric function is distributed along each chromosome) might be expected to show karyotypic instability. This is generally not the case, and in Caenorhabditis elegans, it has been proposed that the role of maintenance of a stable karyotype has been transferred to the meiotic pairing centers, which are found at one end of each chromosome. Here, we explore the phylogenetic stability of nematode chromosomes using a new telomere-to-telomere assembly of the rhabditine nematode Oscheius tipulae generated from nanopore long reads. The 60-Mb O. tipulae genome is resolved into six chromosomal molecules. We find the evidence of specific chromatin diminution at all telomeres. Comparing this chromosomal O. tipulae assembly with chromosomal assemblies of diverse rhabditid nematodes, we identify seven ancestral chromosomal elements (Nigon elements) and present a model for the evolution of nematode chromosomes through rearrangement and fusion of these elements. We identify frequent fusion events involving NigonX, the element associated with the rhabditid X chromosome, and thus sex chromosome-associated gene sets differ markedly between species. Despite the karyotypic stability, gene order within chromosomes defined by Nigon elements is not conserved. Our model for nematode chromosome evolution provides a platform for investigation of the tensions between local genome rearrangement and karyotypic evolution in generating extant genome architectures.
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Milani, Diogo, Vanessa Bardella, Ana Ferretti, Octavio Palacios-Gimenez, Adriana Melo, Rita Moura, Vilma Loreto, Hojun Song, and Diogo Cabral-de-Mello. "Satellite DNAs Unveil Clues about the Ancestry and Composition of B Chromosomes in Three Grasshopper Species." Genes 9, no. 11 (October 26, 2018): 523. http://dx.doi.org/10.3390/genes9110523.
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Supernumerary (B) chromosomes are dispensable genomic elements occurring frequently among grasshoppers. Most B chromosomes are enriched with repetitive DNAs, including satellite DNAs (satDNAs) that could be implicated in their evolution. Although studied in some species, the specific ancestry of B chromosomes is difficult to ascertain and it was determined in only a few examples. Here we used bioinformatics and cytogenetics to characterize the composition and putative ancestry of B chromosomes in three grasshopper species, Rhammatocerus brasiliensis, Schistocerca rubiginosa, and Xyleus discoideus angulatus. Using the RepeatExplorer pipeline we searched for the most abundant satDNAs in Illumina sequenced reads, and then we generated probes used in fluorescent in situ hybridization (FISH) to determine chromosomal position. We used this information to infer ancestry and the events that likely occurred at the origin of B chromosomes. We found twelve, nine, and eighteen satDNA families in the genomes of R. brasiliensis, S. rubiginosa, and X. d. angulatus, respectively. Some satDNAs revealed clustered organization on A and B chromosomes varying in number of sites and position along chromosomes. We did not find specific satDNA occurring in the B chromosome. The satDNAs shared among A and B chromosomes support the idea of putative intraspecific ancestry from small autosomes in the three species, i.e., pair S11 in R. brasiliensis, pair S9 in S. rubiginosa, and pair S10 in X. d. angulatus. The possibility of involvement of other chromosomal pairs in B chromosome origin is also hypothesized. Finally, we discussed particular aspects in composition, origin, and evolution of the B chromosome for each species.
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Vieira, Cristina P., Paula A. Coelho, and Jorge Vieira. "Inferences on the Evolutionary History of theDrosophila americanaPolymorphicX/4Fusion From Patterns of Polymorphism at theX-LinkedparalyticandelavGenes." Genetics 164, no. 4 (August 1, 2003): 1459–69. http://dx.doi.org/10.1093/genetics/164.4.1459.
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AbstractIn Drosophila there is limited evidence on the nature of evolutionary forces affecting chromosomal arrangements other than inversions. The study of the X/4 fusion polymorphism of Drosophila americana is thus of interest. Polymorphism patterns at the paralytic (para) gene, located at the base of the X chromosome, suggest that there is suppressed crossing over in this region between fusion and nonfusion chromosomes but not within fusion and nonfusion chromosomes. These data are thus compatible with previous claims that within fusion chromosomes the amino acid clines found at fused1 (also located at the base of the X chromosome) are likely maintained by local selection. The para data set also suggests a young age of the X/4 fusion. Polymorphism data on para and elav (located at the middle region of the X chromosome) suggest that there is no population structure other than that caused by the X/4 fusion itself. These findings are therefore compatible with previous claims that selection maintains the strong association observed between the methionine/threonine variants at fused1 and the status of the X chromosome as fused or unfused to the fourth chromosome.
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VIEIRA, CRISTINA P., ANDRÉ ALMEIDA, JOÃO DANIEL DIAS, and JORGE VIEIRA. "On the location of the gene(s) harbouring the advantageous variant that maintains the X/4 fusion of Drosophila americana." Genetical Research 87, no. 3 (June 2006): 163–74. http://dx.doi.org/10.1017/s0016672306008147.
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Weak selection is maintaining the Drosophila americana X/4 fusion chromosomal frequency cline. The gene(s) harbouring the advantageous variant(s) that is responsible for the establishment and maintenance of this chromosomal frequency gradient must be located in a region of the X and/or 4th chromosome that is genetically isolated between the X/4 fusion and non-fusion forms. The limits of these regions must thus be determined before an attempt is made to identify these genes. For this purpose, the correspondence between the D. virilis X and 4th chromosome genome scaffolds sequence and the D. americana gene order was established. Polymorphism levels and patterns at seven genes located at the base of the D. americana X chromosome, as well as three genes located at the base of the 4th chromosome, were analysed. The data suggest that the D. americana X/4 fusion is no more than 29000 years old. At the base of the X chromosome, there is suppression of recombination within X/4 fusion and non-fusion chromosomes, and little recombination between the two chromosomal forms. Apparent fixed silent and replacement differences are found in three of seven genes analysed located at the base of the X chromosome. There is no evidence for suppression of recombination between fusion and non-fusion chromosomes at the base of the 4th chromosome. The advantageous variant responsible for the establishment in frequency and maintenance of the X/4 fusion is thus inferred to be in the D. americana X centromere–inversion Xc basal breakpoint region.
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Ayoub Bhatti, Arshad, and Manvi Khajuria. "Karyotypic and Morphometric Analysis of A Predatory Rove Beetle, Paederus littoralis (Coleoptera: Staphylinidae) from Jammu Region of Outer Himalayas, India." Biosciences, Biotechnology Research Asia 15, no. 2 (June 28, 2018): 495–99. http://dx.doi.org/10.13005/bbra/2654.
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In the present study, the chromosomes of a predatory rove beetle Paederus littoralis were studied from Jammu region of outer Himalayas. These beetles are also potential bio-control agents in suppressing the populations of cereal aphids. The diploid chromosome number was found to be 2n=32 including 22 metacentric, 3 submetacentric, 6 subtelocentric and 1 telocentric chromosomes. The sex chromosomes (Xyp) included submetacentric X and telocentric y chromosome. Meiotic observations comprised diplotene, diakinesis and metaphase-I. The study is helpful in solving taxonomic problems with in the family Staphylinidae and it authenticates the existence of this particular species through chromosomal data.
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Meneely, Philip M., Anna F. Farago, and Tate M. Kauffman. "Crossover Distribution and High Interference for Both the X Chromosome and an Autosome During Oogenesis and Spermatogenesis in Caenorhabditis elegans." Genetics 162, no. 3 (November 1, 2002): 1169–77. http://dx.doi.org/10.1093/genetics/162.3.1169.
Full textAbstract:
Abstract Regulation of both the number and the location of crossovers during meiosis is important for normal chromosome segregation. We used sequence-tagged site polymorphisms to examine the distribution of all crossovers on the X chromosome during oogenesis and on one autosome during both oogenesis and spermatogenesis in Caenorhabditis elegans. The X chromosome has essentially one crossover during oogenesis, with only three possible double crossover exceptions among 220 recombinant X chromosomes. All three had one of the two crossovers in the same chromosomal interval, suggesting that crossovers in that interval do not cause interference. No other interval was associated with double crossovers. Very high interference was also found on an autosome during oogenesis, implying that each chromosome has only one crossover during oogenesis. During spermatogenesis, recombination on this autosome was reduced by ∼30% compared to oogenesis, but the relative distribution of the residual crossovers was only slightly different. In contrast to previous results with other autosomes, no double crossover chromosomes were observed. Despite an increased frequency of nonrecombinant chromosomes, segregation of a nonrecombinant autosome during spermatogenesis appears to occur normally. This indicates that an achiasmate segregation system helps to ensure faithful disjunction of autosomes during spermatogenesis.
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Rastan, Sohaila, and Elizabeth J. Robertson. "X-chromosome deletions in embryo-derived (EK) cell lines associated with lack of X-chromosome inactivation." Development 90, no. 1 (December 1, 1985): 379–88. http://dx.doi.org/10.1242/dev.90.1.379.
Full textAbstract:
The predictions of a model for the initiation of X-chromosome inactivation based on a single inactivation centre were tested in a cytogenetic study using six different embryo-derived (EK) stem cell lines, each with a different-sized deletion of the distal part of one of the X-chromosomes. Metaphase chromosomes were prepared by the Kanda method from each cell line in the undifferentiated state and after induction of differentiation, and cytogenetic evidence sought for a dark-staining inactive X-chromosome. The results confirm the predictions of the model in that when the inactivation centre is deleted from one of the X-chromosomes neither X present in a diploid cell can be inactivated, and in addition considerably further localize the position of the inactivation centre on the X-chromosome.
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Meyer, Barbara J. "Sex and death: from cell fate specification to dynamic control of X-chromosome structure and gene expression." Molecular Biology of the Cell 29, no. 22 (November 2018): 2616–21. http://dx.doi.org/10.1091/mbc.e18-06-0397.
Full textAbstract:
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.
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Rovatsos, Michail, Juan Alberto Marchal, Eva Giagia-Athanasopoulou, and Antonio Sánchez. "Molecular Composition of Heterochromatin and Its Contribution to Chromosome Variation in the Microtus thomasi/Microtus atticus Species Complex." Genes 12, no. 6 (May 25, 2021): 807. http://dx.doi.org/10.3390/genes12060807.
Full textAbstract:
The voles of the Microtus thomasi/M. atticus species complex demonstrate a remarkable variability in diploid chromosomal number (2n = 38–44 chromosomes) and sex chromosome morphology. In the current study, we examined by in situ hybridization the topology of four satellite DNA motifs (Msat-160, Mth-Alu900, Mth-Alu2.2, TTAGGG telomeric sequences) and two transposons (LINE, SINE) on the karyotypes of nine chromosome races (i.e., populations with unique cytogenetic traits) of Microtus thomasi, and two chromosomal races of M. atticus. According to the topology of the repetitive DNA motifs, we were able to identify six types of biarmed chromosomes formed from either Robertsonian or/and tandem fusions. In addition, we identified 14 X chromosome variants and 12 Y chromosome variants, and we were able to reconstruct their evolutionary relations, caused mainly by distinct mechanisms of amplification of repetitive DNA elements, including the telomeric sequences. Our study used the model of the Microtus thomasi/M. atticus species complex to explore how repetitive centromeric content can alter from chromosomal rearrangements and can shape the morphology of sex chromosomes, resulting in extensive inter-species cytogenetic variability.
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Gschwend, Andrea R., Qingyi Yu, Paul Moore, Christopher Saski, Cuixia Chen, Jianping Wang, Jong-Kuk Na, and Ray Ming. "Construction of Papaya Male and Female BAC Libraries and Application in Physical Mapping of the Sex Chromosomes." Journal of Biomedicine and Biotechnology 2011 (2011): 1–7. http://dx.doi.org/10.1155/2011/929472.
Full textAbstract:
Papaya is a major fruit crop in the tropics and has recently evolved sex chromosomes. Towards sequencing the papaya sex chromosomes, two bacterial artificial chromosome (BAC) libraries were constructed from papaya male and female genomic DNA. The female BAC library was constructed using restriction enzymeBstY I and consists of 36,864 clones with an average insert size of 104 kb, providing 10.3x genome equivalents. The male BAC library was constructed using restriction enzymeEcoR I and consists of 55,296 clones with an average insert size of 101 kb, providing 15.0x genome equivalents. The male BAC library was used in constructing the physical map of the male-specific region of the male Y chromosome (MSY) and in filling gaps and extending the physical map of the hermaphrodite-specific region of the Yhchromosome (HSY) and the X chromosome physical map. The female BAC library was used to extend the X physical map gap. The MSY, HSY, and X physical maps offer a unique opportunity to study chromosomal rearrangements, Y chromosome degeneration, and dosage compensation of the papaya nascent sex chromosomes.
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McLaren, Anne, Elizabeth Simpson, Colin E. Bishop, Michael J. Mitchell, and Susan M. Darling. "Recombination between the X and Y chromosomes and the Sxr region of the mouse." Genetical Research 60, no. 3 (December 1992): 175–84. http://dx.doi.org/10.1017/s0016672300030925.
Full textAbstract:
SummaryThe Sxr (sex-reversed) region that carries a copy of the mouse Y chromosomal testis-determining gene can be attached to the distal end of either the Y or the X chromosome. During male meiosis, Sxr recombined freely between the X and Y chromosomes, with an estimated recombination frequency not significantly different from 50% in either direction. During female meiosis, Sxr recombined freely between the X chromosome to which it was attached and an X-autosome translocation. A male mouse carrying the original Sxra region on its Y chromosome, and the shorter Sxrb variant on the X, also showed 50% recombination between the sex chromosomes. Evidence of unequal crossing-over between the two Sxr regions was obtained: using five markers deleted from Sxrb, 3 variant Sxr regions were detected in 159 progeny (1·9%). Four other variants (one from the original cross and three from later generations) were presumed to have been derived from illegitimate pairing and crossing-over between Sxrb and the homologous region on the short arm of the Y chromosome. The generation of new variants throws light on the arrangement of gene loci and other markers within the short arm of the mouse Y chromosome.
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Takeda, Masaharu, and Takahito Okushiba. "Reciprocal Chromosome Translocation Between the Left-End 220kb of Chromosome II and the Right-End 270kb of Chromosome X in Saccharomyces cerevisiae." International Journal of Biology 10, no. 4 (July 3, 2018): 1. http://dx.doi.org/10.5539/ijb.v10n4p1.
Full textAbstract:
Southern hybridization of chromosomes and the physical mapping of the genes used as several probes on the respective chromosomes II and X showed that the left-end ca. 220kb of chromosome II including ATP1 was exchanged the right-end ca. 270kb of chromosome X including ATP2 resulting the reciprocal chromosome translocation in the yeast strain YNN290, Saccharomyces cerevisiae. YTO290, the mutated strain by the reciprocal chromosome translocation as above described, was changed from red to white of the colony-color, and sizes of chromosome II lengthened from ca. 830kb to ca. 900kb and chromosome X shortened from ca. 760kb to ca. 690kb, respectively, in compared with the original strain YNN290. But, YTO290 strain was the same as the original strain YNN290 for other properties; the nutrient requiring of the genotype, the ploidy, the mitochondrial respiratory activity, the cell-size, and the growth-rate (doubling time), the number of chromosomes in a cell, It should be as a total number of nucleotides (bases) of genome.ATP1 or ATP2 and their neighboring base sequences respectively should be transferred from chromosome II left-end ca. 220kb to chromosome X right-end or chromosome X right-end ca. 270kb to chromosome II left-end accompanying with this reciprocal chromosome translocation. This mutated (the reciprocal chromosomes II and X translocation = exchanged those end-sequences as above described) strain, YTO290, seemed to lead to decrease the stability of the changed chromosomes II and X. The mutated strain, YTO290 might be observed to go back to the respective chromosomes II and X of the original strain, YNN290, in several months later even at 4°C.
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Ocalewicz, K., and S. Dobosz. "Karyotype variation in the albino rainbow trout (Oncorhynchus mykiss (Walbaum))." Genome 52, no. 4 (April 2009): 347–52. http://dx.doi.org/10.1139/g09-009.
Full textAbstract:
A Robertsonian polymorphism resulting in diploid chromosome number ranging from 59 to 61 and constant chromosome arm number (fundamental number = 104) was observed in the albino rainbow trout ( Oncorhynchus mykiss (Walbaum)) from the yellow color strain. In one individual, 90 mitotic chromosomes and 156 chromosome arms were counted, indicating the fish as a triploid. Morphology of the chromosomes, DAPI staining, and the cytogenetic location of 5S rDNA sequences showed sex-related chromosomal heteromorphism in the specimens. Additionally, length polymorphism of the X chromosome was detected in the studied individuals and two morphs of the X chromosome were described, XL and XS, according to the size of its short arm (p). The XS was observed in the female as well as male albino rainbow trout; however, among females, no XSXS genotype was found. After primed in situ labeling with 5S rDNA primers, the p-arms of both types of the X chromosome showed similar hybridization signals. On the other hand, fluorescence in situ hybridization with telomeric PNA (peptide nucleic acid) probe exhibited weak hybridization spots on the p-arm of the XS chromosome compared with the distinct hybridization spots observed on the XL p-arm. This could reflect a different telomere length on the p-arm of the XS and XL chromosomes. Partial translocation and deletion of the X chromosome p-arm are considered to be responsible for the p-arm length difference between the two morphological variants of X chromosome.
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Luykx, Peter. "Variation in sex-linked interchange heterozygosity in the termite Incisitermes schwarzi Banks (Insecta: Isoptera) on the island of Jamaica." Genome 29, no. 2 (April 1, 1987): 319–25. http://dx.doi.org/10.1139/g87-052.
Full textAbstract:
Collections of colonies of the termite Incisitermes schwarzi from mangroves around the coast of Jamaica revealed six chromosomal types, all involving variations or rearrangements of the sex chromosomes. One of the types had a heteromorphic sex bivalent in which the Y chromosome was larger than the X. The other five races had complex interchange multiples: a chain of 11, a chain of 12, a ring of 12, a ring of 14, and a ring of 18 chromosomes. The situation is similar to that described previously for Kalotermes approximatus, another member of the family Kalotermitidae, in the southeastern United States. The different chromosomal types can be arranged in an evolutionary series, each step requiring an interchange or fusion between an autosome and a previously existing sex chromosome. Such polymorphic chromosome systems, containing Y-segregating elements of different evolutionary ages, may offer an unusual opportunity for studying the sequence of changes accompanying the evolution of Y chromosomes. Key words: termite, Incisitermes, sex-linkage, translocation, interchange, Jamaica.
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Borodin, P. M., M. B. Rogatcheva, K. Koyasu, K. Fukuta, K. Mekada, and S. I. Oda. "Pattern of X–Y chromosome pairing in the Japanese field vole, Microtus montebelli." Genome 40, no. 6 (December 1, 1997): 829–33. http://dx.doi.org/10.1139/g97-807.
Full textAbstract:
Pairing of X and Y chromosomes at meiotic prophase in males of Microtus montebelli was analyzed. The sex chromosomes form a synaptonemal complex at pachytene and end-to-end association at diakinesis – metaphase I in two species of the genus Microtus (M. montebelli and M. oeconomus) only, while they do not pair at all in the other species of this genus that have been studied so far. These data confirm that M. montebelli and M. oeconomus are very closely related in their origin. It is suggested that the sex chromosomes of M. montebelli and M. oeconomus display the ancestral type of X–Y pairing. The lack of X–Y pairing in most species of Microtus appeared after the split in lineage that led to M. oeconomus and M. montebelli on the one hand and the remaining species on the other.Key words: Microtus montebelli, arvicoline phylogeny, synaptic sex chromosome, synaptonemal complex, chromosomal evolution.
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Shetty, Nirmalchandra K. "Inheritance of Chromosomes, Sex Determination, and the Human Genome." Gender and the Genome 2, no. 1 (January 2018): 16–26. http://dx.doi.org/10.1177/2470289718787131.
Full textAbstract:
Who is the determining factor for the sex of the offspring—mother, father, or both parents? This fundamental hypothesis proposes a new model of sex determination, challenging the existing dogma that the male Y chromosome of the father is the sole determinant of the sex of the offspring. According to modern science, the 3 X chromosomes (male XY and female XX) are assumed to be similar, and the sex of the offspring is determined after the zygote is formed. In contrast to this, the new hypothesis based on theoretical research proposes that the 3 X chromosomes can be differentiated, based on the presence of Barr bodies. The first X in female XX chromosomes and X in male XY chromosomes are similar as they lack Barr body and are hereby denoted as ‘X’ and referred to as ancestral chromosomes. The second X chromosome in the female cells which is a Barr body, denoted as X, is different. This X chromosome along with the Y chromosome are referred to as parental chromosomes. Sperm with a Y chromosome can only fuse with an ovum containing the ‘X’ chromosome. Similarly, sperm with the ‘X’ chromosome can only fuse with an ovum containing the X chromosome. Cell biology models of gametogenesis and fertilization were simulated with the new hypothesis model and assessed. Only chromosomes that participated in recombination could unite to form the zygote. This resulted in a paradigm shift in our understanding of sex determination, as both parents were found to be equally responsible for determining the sex of the offspring. The gender of the offspring is determined during the prezygotic stage itself and is dependent on natural selection. A new dimension has been given to inheritance of chromosomes. This new model also presents a new nomenclature for pedigree charts. This work of serendipity may contribute to future research in cell biology, gender studies, genome analysis, and genetic disorders including cancer.
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Gooding, R. H. "Genetic basis of sterility in hybrids from crosses of Glossina morsitans submorsitans and Glossina morsitans morsitans (Diptera: Glossinidae)." Genome 32, no. 3 (June 1, 1989): 479–85. http://dx.doi.org/10.1139/g89-472.
Full textAbstract:
Glossina morsitans submorsitans Newstead and Glossina morsitans morsitans Westwood carrying two marker genes on the X chromosome, two in linkage group II, and one in linkage group III were hybridized. About 17% of the F1 and from 33 to 56% of the backcross males fertilized G. m. submorsitans, but only one F1 and two backcross males fertilized G. m. morsitans. Similarly, F1 and backcross females were fertilized by G. m. submorsitans but rarely by G. m. morsitans. Chromosomal composition of F1 and backcross males indicated that hybrid male sterility is due to incompatibility of the X chromosome from one subspecies and the Y from the other subspecies or possibly an incompatibility between X chromosomes and autosomes from different subspecies. Results are discussed in the context of a model for evolution of X and Y incompatibility and a model for evolution of maternally inherited factors that cause unidirectional sterility in males. In hybrid females, intrachromosomal recombination was suppressed in the X chromosome and in linkage group II. Fertility of backcross females, mated to G. m. submorsitans, could not be related to the chromosomal composition of the females.Key words: Glossina, hybrid sterility, tsetse, X chromosomes.
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Tez, C., Y. Özkul, and O. İbiş. "Karyological comparisons of the European hare (Lepus europaeus Pallas, 1778) from the Asian part of Turkey, with morphological contributions." Archives of Biological Sciences 64, no. 3 (2012): 935–42. http://dx.doi.org/10.2298/abs1203935t.
Full textAbstract:
We focused on a comparison of karyological data for the European brown hare Lepus europaeus, from the Asian part of Turkey. In Turkish L. europaeus, the diploid number (2n), the fundamental number of chromosomal arms (FN) and the number of autosomal arms (FNa) were determined to be 2n=48, 84 and 80, respectively. The autosomes are composed of three pairs of metacentric chromosomes, four pairs of submetacentric chromosomes, ten pairs of subtelocentric chromosomes and six pairs of acrocentric chromosomes. The X chromosome was a medium-large submetacentric and the Y chromosome was a very small acrocentric. This is the third report for L. europaeus from Turkey and confirmed the previous results with regard to 2n. However, when comparing our findings with those of other authors, there were karyotypic differences among the chromosomes. These differences were related to the number of chromosome arms. Additionally, we present the skull measurements of seven samples for the Turkish brown hare collected from three localities, and these measurements conformed to those of previous studies.
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Adler, I. D., R. Johannisson, and H. Winking. "The influence of the Robertsonian translocation Rb(X.2)2Ad on anaphase I non-disjunction in male laboratory mice." Genetical Research 53, no. 2 (April 1989): 77–86. http://dx.doi.org/10.1017/s0016672300027944.
Full textAbstract:
SummaryA Robertsonian translocation in the mouse between theXchromosome and chromosome 2 is described. The male and female carriers of the Rb(X.2)2Ad were fertile. A homozygous/hemizygous line was maintained. The influence of theX-autosomal Robertsonian translocation on anaphase I non-disjunction in male mice was studied by chromosome counts in cells at metaphase II of meoisis and by assessment of aneuploid progeny. The results conclusively show that the inclusion of Rb2Ad in the male genome induces non-disjunction at the first meoitic division. In second metaphase cells the frequency of sex-chromosomal aneuploidy was 10·8%, and secondary spermatocytes containing two or no sex chromosome were equally frequent. The Rb2Ad males sired 3·9% sex-chromosome aneuploid progeny. The difference in aneuploidy frequencies in the germ cells and among the progeny suggests that the viability of XO and XXY individuals is reduced. The pairing configurations of chromosomes 2, Rb2Ad andYwere studied during meiotic prophase by light and electron microscopy. Trivalent pairing was seen in all well spread nuclei. Complete pairing of the acrocentric autosome 2 with the corresponding segment of the Rb2Ad chromosome was only seen in 3·2% of the cells analysed in the electron microscope. The pairing between theXand theYchromosome in the Rb2Ad males corresponded to that in males with normal karyotype. Reasons for sex-chromosomal non-disjunction despite the normal pairing pattern between the sex chromosomes may be seen in the terminal chiasma location coupled with the asynchronous separation of the sex chromosomes and the autosomes. The Rb2Ad chromosome can be useful for studies ofXinactivation, as a marker for parental derivation of theXchromosome and for mapping loci byin situhybridization.
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Murray, A. W., and J. W. Szostak. "Construction and behavior of circularly permuted and telocentric chromosomes in Saccharomyces cerevisiae." Molecular and Cellular Biology 6, no. 9 (September 1986): 3166–72. http://dx.doi.org/10.1128/mcb.6.9.3166.
Full textAbstract:
We developed techniques that allow us to construct novel variants of Saccharomyces cerevisiae chromosomes. These modified chromosomes have precisely determined structures. A metacentric derivative of chromosome III which lacks the telomere-associated X and Y' elements, which are found at the telomeres of most yeast chromosomes, behaves normally in both mitosis and meiosis. We made a circularly permuted telocentric version of yeast chromosome III whose closest telomere was 33 kilobases from the centromere. This telocentric chromosome was lost at a frequency of 1.6 X 10(-5) per cell compared with a frequency of 4.0 X 10(-6) for the natural metacentric version of chromosome III. An extremely telocentric chromosome whose closet telomere was only 3.5 kilobases from the centromere was lost at a frequency of 6.0 X 10(-5). The mitotic stability of telocentric chromosomes shows that the very high frequency of nondisjunction observed for short linear artificial chromosomes is not due to inadequate centromere-telomere separation.
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Murray, A. W., and J. W. Szostak. "Construction and behavior of circularly permuted and telocentric chromosomes in Saccharomyces cerevisiae." Molecular and Cellular Biology 6, no. 9 (September 1986): 3166–72. http://dx.doi.org/10.1128/mcb.6.9.3166-3172.1986.
Full textAbstract:
We developed techniques that allow us to construct novel variants of Saccharomyces cerevisiae chromosomes. These modified chromosomes have precisely determined structures. A metacentric derivative of chromosome III which lacks the telomere-associated X and Y' elements, which are found at the telomeres of most yeast chromosomes, behaves normally in both mitosis and meiosis. We made a circularly permuted telocentric version of yeast chromosome III whose closest telomere was 33 kilobases from the centromere. This telocentric chromosome was lost at a frequency of 1.6 X 10(-5) per cell compared with a frequency of 4.0 X 10(-6) for the natural metacentric version of chromosome III. An extremely telocentric chromosome whose closet telomere was only 3.5 kilobases from the centromere was lost at a frequency of 6.0 X 10(-5). The mitotic stability of telocentric chromosomes shows that the very high frequency of nondisjunction observed for short linear artificial chromosomes is not due to inadequate centromere-telomere separation.
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Borodin, Pavel M., Margarita B. Rogatcheva, Antonina I. Zhelezova, and Sen-ichi Oda. "Chromosome pairing in inter-racial hybrids of the house musk shrew (Suncus murinus, Insectivora, Soricidae)." Genome 41, no. 1 (February 1, 1998): 79–90. http://dx.doi.org/10.1139/g97-103.
Full textAbstract:
Two chromosome races of the house shrew Suncus murinus that differ from each other for five Robertsonian translocations (8.17, 9.13, 10.12, 11.16, and 14.15), heterochromatic insertions in chromosomes 7 and X, and multiple rearrangements in the Y chromosome were crossed and then intercrossed in captivity to produce a hybrid stock. Electron-microscopic analysis of synaptonemal complexes in fertile and sterile hybrid males was carried out. Meiosis in sterile males did not progress beyond pachytene and was severely disrupted. Meiotic arrest was not determined by structural heterozygosity: heterozygotes for all variant chromosomes distinguishing two parental races were found in both sterile and fertile male hybrids. Fertile hybrids demonstrated an orderly pairing of all chromosomes. In heterozygotes for Robertsonian fusions, completely paired trivalents were formed between the Robertsonian metacentrics and homologous acrocentrics. In heterozygotes for chromosome 7, bivalents with a small buckle were observed in a small fraction of pachytene cells. No differences were found in the morphology and pairing pattern of sex bivalents, composed of the X and Y chromosomes derived from the same or different parental races. Univalents, multivalents, and associations between X and Y chromosomes and autosomal trivalents, as well as associations of autosomal trivalents with each other, were observed in a small fraction of the pachytene cells of fertile males. Our results indicate that the system controlling male sterility in interracial hybrids of S. murinus is of genic rather than of chromosomal type.
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Kus, Arita, Joanna Szymanowska-Pułka, Jolanta Kwasniewska, and Robert Hasterok. "Detecting Brachypodium distachyon Chromosomes Bd4 and Bd5 in MH- and X-Ray-Induced Micronuclei Using mcFISH." International Journal of Molecular Sciences 20, no. 11 (June 11, 2019): 2848. http://dx.doi.org/10.3390/ijms20112848.
Full textAbstract:
Micronuclei are biomarkers of genotoxic effects and chromosomal instability. They are formed when chromosome fragments or whole chromosomes fail to disjoin into daughter nuclei. We present qualitative and quantitative analyses of the involvement of specific chromosome regions of chromosomes Bd4 and Bd5 in the formation of micronuclei of Brachypodium distachyon root tip cells following maleic hydrazide (MH) treatment and X-radiation. This is visualised by cytomolecular approaches using bacterial artificial chromosome (BAC)-based multicolour fluorescence in situ hybridisation (mcFISH) in combination with 5S and 25S rDNA probes. The results showed that the long arm of submetacentric chromosome Bd4 forms micronuclei at twice the frequency of its short arm, suggesting that the former is more prone to double-strand breaks (DSBs). In contrast, no difference was observed in the frequency of micronuclei derived from the long and short arms of submetacentric chromosome Bd5. Interestingly, the proximal region of the short arm of Bd5 is more prone to DSBs than its distal part. This demonstrates that 5S rDNA and 35S rDNA loci are not “hot spots” for DNA breaks after the application of these mutagens.
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Rudd, M. Katharine, Robert W. Mays, Stuart Schwartz, and Huntington F. Willard. "Human Artificial Chromosomes with Alpha Satellite-Based De Novo Centromeres Show Increased Frequency of Nondisjunction and Anaphase Lag." Molecular and Cellular Biology 23, no. 21 (November 1, 2003): 7689–97. http://dx.doi.org/10.1128/mcb.23.21.7689-7697.2003.
Full textAbstract:
ABSTRACT Human artificial chromosomes have been used to model requirements for human chromosome segregation and to explore the nature of sequences competent for centromere function. Normal human centromeres require specialized chromatin that consists of alpha satellite DNA complexed with epigenetically modified histones and centromere-specific proteins. While several types of alpha satellite DNA have been used to assemble de novo centromeres in artificial chromosome assays, the extent to which they fully recapitulate normal centromere function has not been explored. Here, we have used two kinds of alpha satellite DNA, DXZ1 (from the X chromosome) and D17Z1 (from chromosome 17), to generate human artificial chromosomes. Although artificial chromosomes are mitotically stable over many months in culture, when we examined their segregation in individual cell divisions using an anaphase assay, artificial chromosomes exhibited more segregation errors than natural human chromosomes (P < 0.001). Naturally occurring, but abnormal small ring chromosomes derived from chromosome 17 and the X chromosome also missegregate more than normal chromosomes, implicating overall chromosome size and/or structure in the fidelity of chromosome segregation. As different artificial chromosomes missegregate over a fivefold range, the data suggest that variable centromeric DNA content and/or epigenetic assembly can influence the mitotic behavior of artificial chromosomes.
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Schartl, M. "A sex chromosomal restriction-fragment-length marker linked to melanoma-determining Tu loci in Xiphophorus." Genetics 119, no. 3 (July 1, 1988): 679–85. http://dx.doi.org/10.1093/genetics/119.3.679.
Full textAbstract:
Abstract In Xiphophorus, the causative genetic information for melanoma formation has been assigned by classical genetics to chromosomal loci, which are located on the sex chromosomes. In our attempts to molecularly clone these melanoma-determining loci, named Tu, we have looked for restriction-fragment-length markers (RFLMs) linked to the Tu loci. These RFLMs should be useful in obtaining a physical map of a Tu locus, which will aid in the cloning of the corresponding sequences. DNA samples from various Xiphophorus strains and hybrids including those bearing different Tu wild-type, deletion and translocation chromosomes, were screened for the presence of random RFLMs using homologous or heterologous sequences as hybridization probes. We find an EcoRI restriction fragment which shows limited crosshybridization to the v-erb B gene--but not representing the authentic c-erb B gene of Xiphophorus--to be polymorphic with respect to different sex chromosomes. Linkage analysis revealed that a 5-kb fragment is linked to the Tu-Sd locus on the X chromosome, a 7-kb fragment is linked to the Tu-Sr locus on the Y chromosome, both of Xiphophorus maculatus, and that a 12-kb fragment is linked to the Tu-Li locus on the X chromosome of Xiphophorus variatus. Using different chromosomal mutants this RFLM has been mapped to a frequent deletion/translocation breakpoint of the X chromosome, less than 0.3 cM apart from the Tu locus.
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KULKARNI, ARPITA, ANNA DYKA, LINDA NEMETSCHKE, WARWICK N. GRANT, and ADRIAN STREIT. "Parastrongyloides trichosuri suggests that XX/XO sex determination is ancestral in Strongyloididae (Nematoda)." Parasitology 140, no. 14 (August 19, 2013): 1822–30. http://dx.doi.org/10.1017/s0031182013001315.
Full textAbstract:
SUMMARYThe parasitic roundworms Strongyloides stercoralis (in man) and Strongyloides ratti (in rats) employ environmentally controlled XX/XO sex determination with a pair of X chromosomes and two pairs of autosomes. Strongyloides papillosus (in sheep) has only two pairs of chromosomes, one of which combines the genetic material homologous to the S. ratti chromosomes X and I. This species creates males through the elimination of one copy of the portion related to the X chromosome (chromatin diminution). It is not clear which one of these two sex-determining mechanisms is ancestral. We demonstrate that Strongyloides vituli (in cattle) has two pairs of chromosomes like its very close relative S. papillosus whereas Parastrongyloides trichosuri, a closely related out-group to Strongyloides spp. in Australian brushtail possums, has three chromosome pairs and employs XX/XO sex determination. The X chromosome of P. trichosuri is homologous to the X chromosome of S. ratti. Our data strongly suggest that the last common ancestor of Strongyloides spp. and Parastrongyloides spp. had two pairs of autosomes along with two or one X chromosome in females and males, respectively. The situation with two pairs of chromosomes is likely derived and occurred through the fusion of the X chromosome with an autosome.
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de Saint Phalle, B., and W. Sullivan. "Incomplete sister chromatid separation is the mechanism of programmed chromosome elimination during early Sciara coprophila embryogenesis." Development 122, no. 12 (December 1, 1996): 3775–84. http://dx.doi.org/10.1242/dev.122.12.3775.
Full textAbstract:
Sex in Sciara coprophila is determined by maternally supplied factors that control the number of paternal X chromosomes eliminated during the syncytial embryonic divisions. Confocal microscopy and FISH demonstrate that the centromeres of the X chromosomes separate at anaphase and remain functional during the cycle in which the X chromosomes are eliminated. However, a region of the sister chromatids fails to separate and the X chromosomes remain at the metaphase plate. This indicates that failure of sister chromatid separation is the mechanism of chromosome elimination. Elimination of the X chromosomes requires the presence of a previously discovered Controlling Element that acts in cis during male meiosis. Using an X-autosome translocation, we demonstrate that the Controlling Element acts at-a-distance to prevent sister chromatid separation in the arm of an autosome. This indicates that the region in which sister chromatid separation fails is chromosome-independent. Although chromosome elimination occurs in all somatic nuclei and is independent of location of the nuclei within the embryo, the decision to eliminate is made at the level of the individual nucleus. Programmed X chromosome elimination occurs at different cycles in male and female embryos. These observations support a model in which elements on the X chromosome are titrating maternally supplied factors controlling the separation of sister X chromatids.
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Ikawa, T., A. Kakegawa, T. Nagano, H. Ando, Y. Yamakoshi, T. Tanabe, J. P. Simmer, C. C. Hu, M. Fukae, and S. Oida. "Porcine Amelogenin is Expressed from the X and Y Chromosomes." Journal of Dental Research 84, no. 2 (February 2005): 144–48. http://dx.doi.org/10.1177/154405910508400207.
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Amelogenin is the major enamel matrix component in developing teeth. In eutherian mammals, amelogenin is expressed from the X chromosome only, or from both the X and Y chromosomes. Two classes of porcine amelogenin cDNA clones have been characterized, but the chromosomal localization of the gene(s) encoding them is unknown. To determine if there are sex-based differences in the expression of porcine amelogenin, we paired PCR primers for exons 1a, 1b, 7a, and 7b, and amplified enamel organ-derived cDNA separately from porcine males and females. The results show that exons 1a/2a and 7a are always together and can be amplified from both males (XY) and females (XX). Exons 1b/2b and 7b are also always paired, but can be amplified only from females. We conclude that porcine amelogenin is expressed from separate genes on the X and Y chromosomes, and not, as previously proposed, from a single gene with two promoters.
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Semeshin, V. F., I. F. Zhimulev, D. Kritikou, and A. Zacharopoulou. "Electron microscope investigation of polytene chromosomes in the Mediterranean fruit fly Ceratitis capitata." Genome 38, no. 4 (August 1, 1995): 652–60. http://dx.doi.org/10.1139/g95-083.
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Ultrastructural analyses of polytene chromosomes from male pupal orbital bristle cells and from larval salivary glands of Ceratitis capitata were carried out. It was shown that chromatin complexes corresponding to the X chromosome heterochromatic network are surrounded by material containing ribonucleoprotein (RNP) granules 250–300 Å (1 Å = 0.1 nm) in diameter. RNP granules of similar size surround the spherical Y chromosome. These data point out the presence of transcriptional activity in both of these chromosomes. The absence of clear structure in chromosomal regions situated between large bands in both types of tissues was observed. These results support the hypothesis of weak synapsis between chromatids or small chromomeres of polytene chromosomes in this species. In addition, we describe a specific puff revealed in both orbital trichogen cells and salivary glands that is morphologically similar to the 93D puff of Drosophila melanogaster.Key words: Ceratitis capitata, polytene chromosomes, electron microscopy.
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FRANTZ, ADRIEN, MANUEL PLANTEGENEST, JOËL BONHOMME, NATHALIE PRUNIER-LETERME, and JEAN-CHRISTOPHE SIMON. "Strong biases in the transmission of sex chromosomes in the aphid Rhopalosiphum padi." Genetical Research 85, no. 2 (April 2005): 111–17. http://dx.doi.org/10.1017/s0016672305007482.
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The typical life cycle of aphids involves several parthenogenetic generations followed by a single sexual one in autumn, i.e. cyclical parthenogenesis. Sexual females are genetically identical to their parthenogenetic mothers and carry two sex chromosomes (XX). Male production involves the elimination of one sex chromosome (to produce X0) that could give rise to genetic conflicts between X-chromosomes. In addition, deleterious recessive mutations could accumulate on sex chromosomes during the parthenogenetic phase and affect males differentially depending on the X-chromosome they inherit. Genetic conflicts and deleterious mutations thus may induce transmission bias that could be exaggerated in males. Here, the transmission of X-chromosomes has been studied in the laboratory in two cyclically parthenogenetic lineages of the bird cherry-oat aphid Rhopalosiphum padi. X-chromosome transmission was followed, using X-linked microsatellite loci, at male production in the two lineages and in their hybrids deriving from reciprocal crosses. Genetic analyses revealed non-Mendelian inheritance of X-chromosomes in both parental and hybrid lineages at different steps of male function. Putative mechanisms and evolutionary consequences of non-Mendelian transmission of X-chromosomes to males are discussed.
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Voskuhl, Rhonda R., Amr H. Sawalha, and Yuichiro Itoh. "Sex chromosome contributions to sex differences in multiple sclerosis susceptibility and progression." Multiple Sclerosis Journal 24, no. 1 (January 2018): 22–31. http://dx.doi.org/10.1177/1352458517737394.
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Background: Why are women more susceptible to multiple sclerosis, but men have worse disability progression? Sex differences in disease may be due to sex hormones, sex chromosomes, or both. Objective: Determine whether differences in sex chromosomes can contribute to sex differences in multiple sclerosis using experimental autoimmune encephalomyelitis. Methods: Sex chromosome transgenic mice, which permit the study of sex chromosomes not confounded by differences in sex hormones, were used to examine an effect of sex chromosomes on autoimmunity and neurodegeneration, focusing on X chromosome genes. Results: T-lymphocyte DNA methylation studies of the X chromosome gene Foxp3 suggested that maternal versus paternal imprinting of X chromosome genes may underlie sex differences in autoimmunity. Bone marrow chimeras with the same immune system but different sex chromosomes in the central nervous system suggested that differential expression of the X chromosome gene Toll-like receptor 7 in neurons may contribute to sex differences in neurodegeneration. Conclusion: Mapping the transcriptome and methylome in T lymphocytes and neurons in females versus males could reveal mechanisms underlying sex differences in autoimmunity and neurodegeneration.
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Frankham, R. "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 33, no. 3 (June 1, 1990): 340–47. http://dx.doi.org/10.1139/g90-053.
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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.
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Hirai, H., I. Tada, H. Takahashi, B. E. B. Nwoke, and G. O. Ufomadu. "Chromosomes of Onchocerca volvulus (Spirurida:Onchocercidae): A comparative study between Nigeria and Guatemala." Journal of Helminthology 61, no. 1 (March 1987): 43–46. http://dx.doi.org/10.1017/s0022149x0000969x.
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ABSTRACTChromosomes of Nigerian Onchocerca volvulus were compared with those of Guatemalan O. volvulus. Both parasites had basically the same chromosomal construct (2n=8, XY type). Autosomes consisted of a pair of large and two smaller pairs. Sex chromosomes were made up of medium sized X chromosome and very small Y chromosome. It was not possible to infer the position of the centromeres.
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Eanes, Walter F., Jody Hey, and David Houle. "HOMOZYGOUS AND HEMIZYGOUS VIABILITY VARIATION ON THE X CHROMOSOME OF DROSOPHILA MELANOGASTER." Genetics 111, no. 4 (December 1, 1985): 831–44. http://dx.doi.org/10.1093/genetics/111.4.831.
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ABSTRACT We report here a study of viability inbreeding depression associated with the X chromosome of Drosophila melanogaster. Fifty wild chromosomes from Mt. Sinai, New York, and 90 wild chromosomes from Death Valley, California, were extracted using the marked FM6 balancer chromosome and viabilities measured for homozygous and heterozygous females, and for hemizygous males, relative to FM6 males as a standard genotype. No statistically significant female genetic load was observed for either chromosome set, although a 95% confidence limit estimated the total load <0.046 for the samples pooled. About 10% of the Death Valley chromosomes appear to be "supervital" as homozygotes. There is little evidence for a pervasive sex-limited detrimental load on the X chromosome; the evidence indicates nearly identical viability effects in males and homozygous females excluding the supervital chromosomes. The average degree of dominance for viability polygenes is estimated between 0.23 to 0.36, which is consistent with autosomal variation and implies near additivity. We conclude that there is little genetic load associated with viability variation on the X chromosome and that the substantial reduction in total fitness observed for chromosome homozygosity in an earlier study may be due largely to sex-limited fertility in females.