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Journal articles on the topic 'Sexual chromosome'
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1
Anderson, Nathan W., Carl E. Hjelmen, and Heath Blackmon. "The probability of fusions joining sex chromosomes and autosomes." Biology Letters 16, no. 11 (November 2020): 20200648. http://dx.doi.org/10.1098/rsbl.2020.0648.
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Chromosome fusion and fission are primary mechanisms of karyotype evolution. In particular, the fusion of a sex chromosome and an autosome has been proposed as a mechanism to resolve intralocus sexual antagonism. If sexual antagonism is common throughout the genome, we should expect to see an excess of fusions that join sex chromosomes and autosomes. Here, we present a null model that provides the probability of a sex chromosome autosome fusion, assuming all chromosomes have an equal probability of being involved in a fusion. This closed-form expression is applicable to both male and female heterogametic sex chromosome systems and can accommodate unequal proportions of fusions originating in males and females. We find that over 25% of all chromosomal fusions are expected to join a sex chromosome and an autosome whenever the diploid autosome count is fewer than 16, regardless of the sex chromosome system. We also demonstrate the utility of our model by analysing two contrasting empirical datasets: one from Drosophila and one from the jumping spider genus Habronattus . We find that in the case of Habronattus , there is a significant excess of sex chromosome autosome fusions but that in Drosophila there are far fewer sex chromosome autosome fusions than would be expected under our null model.
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Liu, Wan-Sheng. "Mammalian Sex Chromosome Structure, Gene Content, and Function in Male Fertility." Annual Review of Animal Biosciences 7, no. 1 (February 15, 2019): 103–24. http://dx.doi.org/10.1146/annurev-animal-020518-115332.
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Mammalian sex chromosomes evolved from an ordinary pair of autosomes. The X chromosome is highly conserved, whereas the Y chromosome varies among species in size, structure, and gene content. Unlike autosomes that contain randomly mixed collections of genes, the sex chromosomes are enriched in testis-biased genes related to sexual development and reproduction, particularly in spermatogenesis and male fertility. This review focuses on how sex chromosome dosage compensation takes place and why meiotic sex chromosome inactivation occurs during spermatogenesis. Furthermore, the review also emphasizes how testis-biased genes are enriched on the sex chromosomes and their functions in male fertility. It is concluded that sex chromosomes are critical to sexual development and male fertility; however, our understanding of how sex chromosome genes direct sexual development and fertility has been hampered by the structural complexities of the sex chromosomes and by the multicopy nature of the testis gene families that also play a role in immunity, cancer development, and brain function.
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Li, Yiyuan, Bo Zhang, and Nancy A. Moran. "The Aphid X Chromosome Is a Dangerous Place for Functionally Important Genes: Diverse Evolution of Hemipteran Genomes Based on Chromosome-Level Assemblies." Molecular Biology and Evolution 37, no. 8 (April 14, 2020): 2357–68. http://dx.doi.org/10.1093/molbev/msaa095.
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Abstract Different evolutionary forces shape gene content and sequence evolution on autosomes versus sex chromosomes. Location on a sex chromosome can favor male-beneficial or female-beneficial mutations depending on the sex determination system and selective pressure on different sexual morphs. An X0 sex determination can lead to autosomal enrichment of male-biased genes, as observed in some hemipteran insect species. Aphids share X0 sex determination; however, models predict the opposite pattern, due to their unusual life cycles, which alternate between all-female asexual generations and a single sexual generation. Predictions include enrichment of female-biased genes on autosomes and of male-biased genes on the X, in contrast to expectations for obligately sexual species. Robust tests of these models require chromosome-level genome assemblies for aphids and related hemipterans with X0 sex determination and obligate sexual reproduction. In this study, we built the first chromosome-level assembly of a psyllid, an aphid relative with X0 sex determination and obligate sexuality, and compared it with recently resolved chromosome-level assemblies of aphid genomes. Aphid and psyllid X chromosomes differ strikingly. In aphids, female-biased genes are strongly enriched on autosomes and male-biased genes are enriched on the X. In psyllids, male-biased genes are enriched on autosomes. Furthermore, functionally important gene categories of aphids are enriched on autosomes. Aphid X-linked genes and male-biased genes are under relaxed purifying selection, but gene content and order on the X is highly conserved, possibly reflecting constraints imposed by unique chromosomal mechanisms associated with the unusual aphid life cycle.
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Filippova, V. V. "Shereshevsky–Turner Syndrome is a natural model of primary hypogonadism in girls (a clinical case)." Public health of the Far East Peer-reviewed scientific and practical journal 94, no. 4 (December 23, 2022): 60–64. http://dx.doi.org/10.33454/1728-1261-2022-4-60-64.
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Shereshevsky-Turner syndrome refers to chromosomal diseases associated with the pathology of sex chromosome. The syndrome is the only viable monosomy (there is only one chromosome from a couple), refers to frequent genomic disorders. At the same time, the lack of recognizable phenotypic symptoms, the gradual development of quite common manifestations (deviations of physical and sexual development) complicates the timely diagnosis of the syndrome. The lag in growth, the formation of secondary sexual characteristics is a factor requiring clarification of the cause. The time of diagnosis is the key to timely therapeutic tactics, which provides an improvement in the quality of life in caae of the pathology of sexual chromosomes, optimal socialization in modern society. The lack of diagnosis does not allow to start the necessary pathogenetic therapy
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Coyne, Jerry A. "Genetics of sexual isolation in male hybrids of Drosophila simulans and D. mauritiana." Genetical Research 68, no. 3 (December 1996): 211–20. http://dx.doi.org/10.1017/s0016672300034182.
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SummarySexual isolation between the sibling species D. simulans and D. mauritiana is due largely to the rejection of D. simulans males by D. mauritiana females. Genetic analysis shows that genes on the X and third chromosomes contribute to the differences between males causing sexual isolation, while the Y chromosome, second chromosome and cytoplasm have no effect. These chromosome effects differ from those observed in a previous analysis of sexual isolation in hybrid females, implying that different genes cause sexual isolation in the two sexes.
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Yadav, Vikas, Sheng Sun, Marco A. Coelho, and Joseph Heitman. "Centromere scission drives chromosome shuffling and reproductive isolation." Proceedings of the National Academy of Sciences 117, no. 14 (March 19, 2020): 7917–28. http://dx.doi.org/10.1073/pnas.1918659117.
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A fundamental characteristic of eukaryotic organisms is the generation of genetic variation via sexual reproduction. Conversely, significant large-scale genome structure variations could hamper sexual reproduction, causing reproductive isolation and promoting speciation. The underlying processes behind large-scale genome rearrangements are not well understood and include chromosome translocations involving centromeres. Recent genomic studies in theCryptococcusspecies complex revealed that chromosome translocations generated via centromere recombination have reshaped the genomes of different species. In this study, multiple DNA double-strand breaks (DSBs) were generated via the CRISPR/Cas9 system at centromere-specific retrotransposons in the human fungal pathogenCryptococcus neoformans. The resulting DSBs were repaired in a complex manner, leading to the formation of multiple interchromosomal rearrangements and new telomeres, similar to chromothripsis-like events. The newly generated strains harboring chromosome translocations exhibited normal vegetative growth but failed to undergo successful sexual reproduction with the parental wild-type strain. One of these strains failed to produce any spores, while another produced ∼3% viable progeny. The germinated progeny exhibited aneuploidy for multiple chromosomes and showed improved fertility with both parents. All chromosome translocation events were accompanied without any detectable change in gene sequences and thus suggest that chromosomal translocations alone may play an underappreciated role in the onset of reproductive isolation and speciation.
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Alton, Michelle, Mau Pan Lau, Michele Villemure, and Teruko Taketo. "The behavior of the X- and Y-chromosomes in the oocyte during meiotic prophase in the B6.YTIR sex-reversed mouse ovary." REPRODUCTION 135, no. 2 (February 2008): 241–52. http://dx.doi.org/10.1530/rep-07-0383.
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Sexual differentiation of the germ cells follows gonadal differentiation, which is determined by the presence or the absence of the Y-chromosome. Consequently, oogenesis and spermatogenesis take place in the germ cells with XX and XY sex chromosomal compositions respectively. It is unclear how sexual dimorphic regulation of meiosis is associated with the sex-chromosomal composition. In the present study, we examined the behavior of the sex chromosomes in the oocytes of the B6.YTIRsex-reversed female mouse, in comparison with XO and XX females. As the sex chromosomes fail to pair in both XY and XO oocytes during meiotic prophase, we anticipated that the pairing failure may lead to excessive oocyte loss. However, the total number of germ cells, identified by immunolabeling of germ cell nuclear antigen 1 (GCNA1), did not differ between XY and XX ovaries or XO and XX ovaries up to the day of delivery. The progression of meiotic prophase, assessed by immunolabeling of synaptonemal complex components, was also similar between the two genotypes of ovaries. These observations suggest that the failure in sex-chromosome pairing is not sufficient to cause oocyte loss. On the other hand, labeling of phosphorylated histone γH2AX, known to be associated with asynapsis and transcriptional repression, was seen over the X-chromosome but not over the Y-chromosome in the majority of XY oocytes at the pachytene stage. For comparison, γH2AX labeling was seen only in the minority of XX oocytes at the same stage. We speculate that the transcriptional activity of sex chromosomes in the XY oocyte may be incompatible with ooplasmic maturation.
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Branco, Sara, Hélène Badouin, Ricardo C. Rodríguez de la Vega, Jérôme Gouzy, Fantin Carpentier, Gabriela Aguileta, Sophie Siguenza, et al. "Evolutionary strata on young mating-type chromosomes despite the lack of sexual antagonism." Proceedings of the National Academy of Sciences 114, no. 27 (June 19, 2017): 7067–72. http://dx.doi.org/10.1073/pnas.1701658114.
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Sex chromosomes can display successive steps of recombination suppression known as “evolutionary strata,” which are thought to result from the successive linkage of sexually antagonistic genes to sex-determining genes. However, there is little evidence to support this explanation. Here we investigate whether evolutionary strata can evolve without sexual antagonism using fungi that display suppressed recombination extending beyond loci determining mating compatibility despite lack of male/female roles associated with their mating types. By comparing full-length chromosome assemblies from five anther-smut fungi with or without recombination suppression in their mating-type chromosomes, we inferred the ancestral gene order and derived chromosomal arrangements in this group. This approach shed light on the chromosomal fusion underlying the linkage of mating-type loci in fungi and provided evidence for multiple clearly resolved evolutionary strata over a range of ages (0.9–2.1 million years) in mating-type chromosomes. Several evolutionary strata did not include genes involved in mating-type determination. The existence of strata devoid of mating-type genes, despite the lack of sexual antagonism, calls for a unified theory of sex-related chromosome evolution, incorporating, for example, the influence of partially linked deleterious mutations and the maintenance of neutral rearrangement polymorphism due to balancing selection on sexes and mating types.
9
Shaw, G., MB Renfree, and RV Short. "Primary Genetic-Control of Sexual-Differentiation in Marsupials." Australian Journal of Zoology 37, no. 3 (1989): 443. http://dx.doi.org/10.1071/zo9890443.
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Marsupials, like eutherians, normally require the presence of a Y chromosome for testicular formation. However some sexually dimorphic characters such as the scrotum, mammary anlagen, gubernaculum and processus vaginalis appear to be under direct genetic rather than secondary hormonal control. Scrota1 development occurs where only a single X chromosome is functional, whilst two X chromosomes are necessary for pouch formation.
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Lardon, André, Sevdalin Georgiev, Abdelmalik Aghmir, Guenaël Le Merrer, and Ioan Negrutiu. "Sexual Dimorphism in White Campion: Complex Control of Carpel Number Is Revealed by Y Chromosome Deletions." Genetics 151, no. 3 (March 1, 1999): 1173–85. http://dx.doi.org/10.1093/genetics/151.3.1173.
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Abstract Sexual dimorphism in the dioecious plant white campion (Silene latifolia = Melandrium album) is under the control of two main regions on the Y chromosome. One such region, encoding the gynoecium-suppressing function (GSF), is responsible for the arrest of carpel initiation in male flowers. To generate chromosomal deletions, we used pollen irradiation in male plants to produce hermaphroditic mutants (bsx mutants) in which carpel development was restored. The mutants resulted from alterations in at least two GSF chromosomal regions, one autosomal and one located on the distal half of the (p)-arm of the Y chromosome. The two mutations affected carpel development independently, each mutation showing incomplete penetrance and variegation, albeit at significantly different levels. During successive meiotic generations, a progressive increase in penetrance and a reduction in variegation levels were observed and quantified at the level of the Y-linked GSF (GSF-Y). Possible mechanisms are proposed to explain the behavior of the bsx mutations: epigenetic regulation or/and second-site mutation of modifier genes. In addition, studies on the inheritance of the hermaphroditic trait showed that, unlike wild-type Y chromosomes, deleted Y chromosomes can be transmitted through both the male and the female lines. Altogether, these findings bring experimental support, on the one hand, to the existence on the Y chromosome of genic meiotic drive function(s) and, on the other hand, to models that consider that dioecy evolved through multiple mutation events. As such, the GSF is actually a system containing more than one locus and whose primary component is located on the Y chromosome.
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Lee, LingSze, Eugenia E. Montiel, Beatriz M. Navarro-Domínguez, and Nicole Valenzuela. "Chromosomal Rearrangements during Turtle Evolution Altered the Synteny of Genes Involved in Vertebrate Sex Determination." Cytogenetic and Genome Research 157, no. 1-2 (2019): 77–88. http://dx.doi.org/10.1159/000497302.
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Sex-determining mechanisms (SDMs) set an individual's sexual fate by its genotype (genotypic sex determination, GSD) or environmental factors like temperature (temperature- dependent sex determination, TSD), as in turtles where the GSD “trigger” remains unknown. SDMs co-evolve with turtle chromosome number, perhaps because fusions/fissions alter the relative position/regulation of sexual development genes. Here, we map 10 such genes via FISH onto metaphase chromosomes in 6 TSD and 6 GSD turtles for the first time. Results uncovered intrachromosomal rearrangements involving 3 genes across SDMs (Dax1, Fhl2, and Fgf9) and a chromosomal fusion linking 2 genes (Sf1 and Rspo1) in 1 chromosome in a TSD turtle (Pelomedusa subrufa) that locate to 2 chromosomes in all others. Notably, Sf1 and its repressor Foxl2 map to Apalone spinifera's ZW chromosomes but to a macro- (Foxl2) and a microautosome (Sf1) in other turtles potentially inducing SDM evolution. However, our phylogenetically informed analysis refutes Foxl2 (but not Sf1) as Apalone's master sex-determining gene. The absence of common TSD-specific or GSD-specific rearrangements underscores the independent evolutionary trajectories of turtle SDMs. Further comparative analyses using more genes from the sexual development network are warranted to inform genome evolution and its contribution to enigmatic turnovers of vertebrate sex determination.
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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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Carey, Sarah B., Jerry Jenkins, John T. Lovell, Florian Maumus, Avinash Sreedasyam, Adam C. Payton, Shengqiang Shu, et al. "Gene-rich UV sex chromosomes harbor conserved regulators of sexual development." Science Advances 7, no. 27 (June 2021): eabh2488. http://dx.doi.org/10.1126/sciadv.abh2488.
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Nonrecombining sex chromosomes, like the mammalian Y, often lose genes and accumulate transposable elements, a process termed degeneration. The correlation between suppressed recombination and degeneration is clear in animal XY systems, but the absence of recombination is confounded with other asymmetries between the X and Y. In contrast, UV sex chromosomes, like those found in bryophytes, experience symmetrical population genetic conditions. Here, we generate nearly gapless female and male chromosome-scale reference genomes of the moss Ceratodon purpureus to test for degeneration in the bryophyte UV sex chromosomes. We show that the moss sex chromosomes evolved over 300 million years ago and expanded via two chromosomal fusions. Although the sex chromosomes exhibit weaker purifying selection than autosomes, we find that suppressed recombination alone is insufficient to drive degeneration. Instead, the U and V sex chromosomes harbor thousands of broadly expressed genes, including numerous key regulators of sexual development across land plants.
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VARNAMKHASTI, MOHAMMAD JALALI, and LAI SOON LEE. "A GENETIC ALGORITHM BASED ON SEXUAL SELECTION FOR THE MULTIDIMENSIONAL 0/1 KNAPSACK PROBLEMS." International Journal of Modern Physics: Conference Series 09 (January 2012): 422–31. http://dx.doi.org/10.1142/s2010194512005508.
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In this study, a new technique is presented for choosing mate chromosomes during sexual selection in a genetic algorithm. The population is divided into groups of males and females. During the sexual selection, the female chromosome is selected by the tournament selection while the male chromosome is selected based on the hamming distance from the selected female chromosome, fitness value or active genes. Computational experiments are conducted on the proposed technique and the results are compared with some selection mechanisms commonly used for solving multidimensional 0/1 knapsack problems published in the literature.
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Sherman, R. A., P. W. Voigt, B. L. Burson, and C. L. Dewald. "Apomixis in diploid × triploid Tripsacum dactyloides hybrids." Genome 34, no. 4 (August 1, 1991): 528–32. http://dx.doi.org/10.1139/g91-081.
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Apomixis can hinder plant improvement if sexual or apomictic germ plasm of the appropriate ploidy level, required for effective manipulation of apomixis, is not available. To develop needed germ plasm and increase knowledge of apomixis in Tripsacum dactyloides, diploid (2n = 2x = 36) sexual plants were crossed with a highly apomictic triploid (2n = 3x = 54) accession in an attempt to transfer apomixis from a polyploid to the diploid level. The fertility of most hybrids was very low, 69% had 10% or less seed set. A selected subset of 48 hybrids, including most of the more fertile plants, was studied cytologically. The chromosome number of these hybrids ranged from 2n = 36 to 2n = 54. All but 3 of 46 of the 48 hybrids showed indications of apomictic development. Those with near-diploid chromosome numbers were primarily sexual. Highly apomictic hybrids, based on percent diplosporous ovules, had 43 or more chromosomes. Fertility of these hybrids was not related to chromosome number. Fertility of sexual to moderately apomictic plants was reduced as chromosome number increased. Apomixis in T. dactyloides is facultative. Backcrosses are needed to develop germ plasm with a high level of apomixis and near-diploid chromosome numbers.Key words: eastern gama-grass, chromosome number, fertility, mode of reproduction, germ plasm.
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Mola, Liliana M., María Florencia Fourastié, and Silvia Susana Agopian. "High karyotypic variation in Orthemis Hagen, 1861 species, with insights about the neo-XY in Orthemis ambinigra Calvert, 1909 (Libellulidae, Odonata)." Comparative Cytogenetics 15, no. 4 (November 3, 2021): 355–74. http://dx.doi.org/10.3897/compcytogen.v15.i4.68761.
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The American dragonfly genus Orthemis Hagen, 1861 is mainly found in the Neotropical region. Seven of 28 taxonomically described species have been reported from Argentina. Chromosome studies performed on this genus showed a wide variation in chromosome number and a high frequency of the neoXY chromosomal sex-determination system, although the sexual pair was not observed in all cases. This work analyzes the spermatogenesis of Orthemis discolor (Burmeister, 1839), O. nodiplaga Karsch, 1891 and O. ambinigra Calvert, 1909 in individuals from the provinces of Misiones and Buenos Aires, Argentina. Orthemis discolor has 2n=23, n=11+X and one larger bivalent. Orthemis nodiplaga exhibits the largest chromosome number of the order, 2n=41, n=20+X and small chromosomes. Orthemis ambinigra shows a reduced complement, 2n=12, n=5+neo-XY, large-sized chromosomes, and a homomorphic sex bivalent. Fusions and fragmentations are the main evolutionary mechanisms in Odonata, as well as in other organisms with holokinetic chromosomes. Orthemis nodiplaga would have originated by nine autosomal fragmentations from the ancestral karyotype of the genus (2n=22A+X in males). We argue that the diploid number 23 in Orthemis has a secondary origin from the ancestral karyotype of family Libellulidae (2n=25). The complement of O. ambinigra would have arisen from five autosomal fusions and the insertion of the X chromosome into a fused autosome. C-banding and DAPI/CMA3 staining allowed the identification of the sexual bivalent, which revealed the presence of constitutive heterochromatin. We propose that the chromosome with intermediate C-staining intensity and three medial heterochromatic regions corresponds to the neo-Y and that the neo-system of this species has an ancient evolutionary origin. Moreover, we discuss on the mechanisms involved in the karyotypic evolution of this genus, the characteristics of the neo sex-determining systems and the patterns of heterochromatin distribution, quantity and base pair richness.
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Furman, Benjamin L. S., Caroline M. S. Cauret, Martin Knytl, Xue-Ying Song, Tharindu Premachandra, Caleb Ofori-Boateng, Danielle C. Jordan, Marko E. Horb, and Ben J. Evans. "A frog with three sex chromosomes that co-mingle together in nature: Xenopus tropicalis has a degenerate W and a Y that evolved from a Z chromosome." PLOS Genetics 16, no. 11 (November 9, 2020): e1009121. http://dx.doi.org/10.1371/journal.pgen.1009121.
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In many species, sexual differentiation is a vital prelude to reproduction, and disruption of this process can have severe fitness effects, including sterility. It is thus interesting that genetic systems governing sexual differentiation vary among—and even within—species. To understand these systems more, we investigated a rare example of a frog with three sex chromosomes: the Western clawed frog, Xenopus tropicalis. We demonstrate that natural populations from the western and eastern edges of Ghana have a young Y chromosome, and that a male-determining factor on this Y chromosome is in a very similar genomic location as a previously known female-determining factor on the W chromosome. Nucleotide polymorphism of expressed transcripts suggests genetic degeneration on the W chromosome, emergence of a new Y chromosome from an ancestral Z chromosome, and natural co-mingling of the W, Z, and Y chromosomes in the same population. Compared to the rest of the genome, a small sex-associated portion of the sex chromosomes has a 50-fold enrichment of transcripts with male-biased expression during early gonadal differentiation. Additionally, X. tropicalis has sex-differences in the rates and genomic locations of recombination events during gametogenesis that are similar to at least two other Xenopus species, which suggests that sex differences in recombination are genus-wide. These findings are consistent with theoretical expectations associated with recombination suppression on sex chromosomes, demonstrate that several characteristics of old and established sex chromosomes (e.g., nucleotide divergence, sex biased expression) can arise well before sex chromosomes become cytogenetically distinguished, and show how these characteristics can have lingering consequences that are carried forward through sex chromosome turnovers.
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Tu, Y. Q., J. Sun, X. H. Ge, and Z. Y. Li. "Production and genetic analysis of partial hybrids from intertribal sexual crosses between Brassica napus and Isatis indigotica and progenies." Genome 53, no. 2 (February 2010): 146–56. http://dx.doi.org/10.1139/g09-093.
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With the dye and medicinal plant Isatis indigotica (2n = 14) as pollen parent, intertribal sexual hybrids with Brassica napus (2n = 38, AACC) were obtained and characterized. Among a lot of F1 plants produced, only five hybrids (H1–H5) were distinguished morphologically from female B. napus parents by showing low fertility and some characters of I. indigotica, and also by having different chromosome numbers. H1–H4 had similar but variable chromosome numbers in their somatic and meiotic cells (2n = 25–30), and H5 had 2n = 19, the same number as the haploid of B. napus. GISH analysis of the cells from H1 and H5 detected one I. indigotica chromosome and one or two chromosome terminal fragments. New B. napus types with phenotypic and genomic alterations were produced by H1 after pollination by B. napus and selfing for several generations, and by H5 after selfing. A progeny plant (2n = 20) was derived from H1 after pollination by I. indigotica twice and had a phenotype similar to a certain type of B. rapa, showing that hybrid H1 likely retained all chromosomes of the A genome and lost some of the C genome in parental B. napus. The reasons for the formation of the partial hybrids with unexpected chromosomal complements and for the chromosome elimination are discussed.
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Larkin, P. J., P. M. Banks, R. Bhati, R. I. S. Brettell, P. A. Davies, S. A. Ryan, W. R. Scowcroft, L. H. Spindler, and G. J. Tanner. "From somatic variation to variant plants: mechanisms and applications." Genome 31, no. 2 (January 15, 1989): 705–11. http://dx.doi.org/10.1139/g89-128.
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Plants from cell cultures show a high incidence of mutation. The causes of somaclonal variation are unknown, but the genetic consequences have been analysed. A range of genetic events are responsible, including single base changes; altered gene copy number; altered expression of multigene families; chromosome fragment interchanges; and mobilisation of transposable elements. Recent applications of these phenomena are discussed in this paper, for example, in vitro selection, somaclonal variation for agronomic traits, and limited gene transfer from cultured sexual and somatic hybrids. Research is outlined attempting to use high frequency chromosomal interchanges in wheat cell cultures to introgress genes from alien chromosomes. Two examples are cereal cyst nematode resistance on a rye chromosome and barley yellow dwarf resistance on a Thinopyrum chromosome. Some presumptive introgressed lines show selfed and backcross segregations, suggesting that the resistance, but not other alien markers, is now on a wheat chromosome.Key words: somaclonal variation, introgression, somatic hybridization, chromosome rearrangement, in vitro selection.
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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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Wolf, Ulrich. "Y-chromosome and Sexual Differentiation." Clinical Genetics 14, no. 5 (April 23, 2008): 314. http://dx.doi.org/10.1111/j.1399-0004.1978.tb02204.x.
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Yamamoto, Ayumu. "Shake It Off: The Elimination of Erroneous Kinetochore-Microtubule Attachments and Chromosome Oscillation." International Journal of Molecular Sciences 22, no. 6 (March 20, 2021): 3174. http://dx.doi.org/10.3390/ijms22063174.
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Cell proliferation and sexual reproduction require the faithful segregation of chromosomes. Chromosome segregation is driven by the interaction of chromosomes with the spindle, and the attachment of chromosomes to the proper spindle poles is essential. Initial attachments are frequently erroneous due to the random nature of the attachment process; however, erroneous attachments are selectively eliminated. Proper attachment generates greater tension at the kinetochore than erroneous attachments, and it is thought that attachment selection is dependent on this tension. However, studies of meiotic chromosome segregation suggest that attachment elimination cannot be solely attributed to tension, and the precise mechanism of selective elimination of erroneous attachments remains unclear. During attachment elimination, chromosomes oscillate between the spindle poles. A recent study on meiotic chromosome segregation in fission yeast has suggested that attachment elimination is coupled to chromosome oscillation. In this review, the possible contribution of chromosome oscillation in the elimination of erroneous attachment is discussed in light of the recent finding.
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Yang, Fen, and Ales Pecinka. "Multiple Roles of SMC5/6 Complex during Plant Sexual Reproduction." International Journal of Molecular Sciences 23, no. 9 (April 19, 2022): 4503. http://dx.doi.org/10.3390/ijms23094503.
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Chromatin-based processes are essential for cellular functions. Structural maintenance of chromosomes (SMCs) are evolutionarily conserved molecular machines that organize chromosomes throughout the cell cycle, mediate chromosome compaction, promote DNA repair, or control sister chromatid attachment. The SMC5/6 complex is known for its pivotal role during the maintenance of genome stability. However, a dozen recent plant studies expanded the repertoire of SMC5/6 complex functions to the entire plant sexual reproductive phase. The SMC5/6 complex is essential in meiosis, where its activity must be precisely regulated to allow for normal meiocyte development. Initially, it is attenuated by the recombinase RAD51 to allow for efficient strand invasion by the meiosis-specific recombinase DMC1. At later stages, it is essential for the normal ratio of interfering and non-interfering crossovers, detoxifying aberrant joint molecules, preventing chromosome fragmentation, and ensuring normal chromosome/sister chromatid segregation. The latter meiotic defects lead to the production of diploid male gametes in Arabidopsis SMC5/6 complex mutants, increased seed abortion, and production of triploid offspring. The SMC5/6 complex is directly involved in controlling normal embryo and endosperm cell divisions, and pioneer studies show that the SMC5/6 complex is also important for seed development and normal plant growth in cereals.
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Lenormand, Thomas, and Denis Roze. "Y recombination arrest and degeneration in the absence of sexual dimorphism." Science 375, no. 6581 (February 11, 2022): 663–66. http://dx.doi.org/10.1126/science.abj1813.
Full textAbstract:
Current theory proposes that degenerated sex chromosomes—such as the mammalian Y—evolve through three steps: (i) recombination arrest, linking male-beneficial alleles to the Y chromosome; (ii) Y degeneration, resulting from the inefficacy of selection in the absence of recombination; and (iii) dosage compensation, correcting the resulting low expression of X-linked genes in males. We investigate a model of sex chromosome evolution that incorporates the coevolution of cis and trans regulators of gene expression. We show that the early emergence of dosage compensation favors the maintenance of Y-linked inversions by creating sex-antagonistic regulatory effects. This is followed by degeneration of these nonrecombining inversions caused by regulatory divergence between the X and Y chromosomes. In contrast to current theory, the whole process occurs without any selective pressure related to sexual dimorphism.
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Oliveira, Renildo Ribeiro de, Issakar Lima Souza, and Paulo Cesar Venere. "Karyotype description of three species of Loricariidae (Siluriformes) and occurrence of the ZZ/ZW sexual system in Hemiancistrus spilomma Cardoso & Lucinda, 2003." Neotropical Ichthyology 4, no. 1 (March 2006): 93–97. http://dx.doi.org/10.1590/s1679-62252006000100010.
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The neotropical freshwater systems have a high number of catfish species (Siluriformes), and many of those are denominated "cascudos" in Brazil. Cytogenetic data about three "cascudos" species fished in the rio Araguaia are described in the present study. The Pterygoplichthys joselimaianus showed 2n=52, with 28 metacentrics (M) chromosomes, 16 submetacentrics (SM) and 8 subtelocentrics/acrocentrics (ST/A) in both sexes. Hemiancistrus spinosissimus showed 2n=52, with karyotype formulae 26M+22SM+4ST, in both sexes. Hemiancistrusspilomma also showed 2n=52, but in this species a ZZ/ZW sex chromosome system (25M+21SM+6ST in females and 24M+22SM+6ST in males) was observed. The cells from H. spinosissimus and P. joselimaianus showed one chromosome pair bearing Ag-NORs, while in the H. spilomma three chromosome pairs bearing Ag-NORs were detected. The data showed in this work reveal particular chromosomal characteristics, important for a good recognition of both Hemincistrus species, and also show the importance of the insertion of cytogenetic data on taxonomic phylogenetic studies.
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Souza, Fernando H. S. de, Francisco de M. C. Sassi, Pedro H. N. Ferreira, Luiz A. C. Bertollo, Tariq Ezaz, Thomas Liehr, Manolo F. Perez, and Marcelo B. Cioffi. "Integrating Cytogenetics and Population Genomics: Allopatry and Neo-Sex Chromosomes May Have Shaped the Genetic Divergence in the Erythrinus erythrinus Species Complex (Teleostei, Characiformes)." Biology 11, no. 2 (February 16, 2022): 315. http://dx.doi.org/10.3390/biology11020315.
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Diversity found in Neotropical freshwater fish is remarkable. It can even hinder a proper delimitation of many species, with the wolf fish Erythrinus erythrinus (Teleostei, Characiformes) being a notable example. This nominal species shows remarkable intra-specific variation, with extensive karyotype diversity found among populations in terms of different diploid chromosome numbers (2n), karyotype compositions and sex chromosome systems. Here, we analyzed three distinct populations (one of them cytogenetically investigated for the first time) that differed in terms of their chromosomal features (termed karyomorphs) and by the presence or absence of heteromorphic sex chromosomes. We combined cytogenetics with genomic approaches to investigate how the evolution of multiple sex chromosomes together with allopatry is linked to genetic diversity and speciation. The results indicated the presence of high genetic differentiation among populations both from cytogenetic and genomic aspects, with long-distance allopatry potentially being the main agent of genetic divergence. One population showed a neo-X1X2Y sexual chromosome system and we hypothesize that this system is associated with enhanced inter-population genetic differentiation which could have potentially accelerated speciation compared to the effect of allopatry alone.
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Paul, Chiranjit, and Bimal Debnath. "A report on new chromosome number of three Dioscorea species." Plant Science Today 6, no. 2 (April 27, 2019): 147–50. http://dx.doi.org/10.14719/pst.2019.6.2.490.
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Chromosomal study conducted in nine species of Dioscorea from different forest belts of Tripura revealed that their somatic chromosome number ranged from 2n=40 to 2n=60. The record of 2n=40 chromosome in the sexual phenotypes of Dioscorea hamiltonii, Dioscorea glabra and Dioscorea pubera are the first time report from Tripura, North East India. Moreover the somatic chromosome counts of 2n=60 in Dioscorea pentaphylla would be attributed as a new cytotype. However at the respective ploidy level no difference in somatic chromosome count was observed between their sexes.
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McDonough, Paul G. "The Y-chromosome and reproductive disorders." Reproduction, Fertility and Development 10, no. 1 (1998): 1. http://dx.doi.org/10.1071/r98033.
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Over the past decade the tools of modern molecular biology have provided unique insights into our fundamental understanding of developmental systems. These insights have been gleaned from the study of a wide variety of model organisms including yeast (Saccharomyces cerevisiae), fly (Drosophila), worm (Caenorhabditis elegans), and mouse. In man, the first analysis of developmental systems started with sexual differentiation and focused on the role of Y-linked genes. The presence of living developmental mutants in man affecting sexual development and the early technology of deletion mapping facilitated the isolation and identification of small segments of putative DNA suspected to contain sex-determining genes. The isolation of genes such as SRY (Sex Related gene on Y) has provided the first insights into the molecular biology of human sexual differentiation. The focus on the Y chromosome has brought further insights into chromosomal pairing, statural determinants in man, oncogenesis, spermatogenesis, haploid genomes, and the lineage of man himself. This paper provides the circumstantial and direct evidence to illustrate the importance of the Y chromosome in reproductive disorders, and in the analysis of haploid genomes.
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Mitiku, Takele, and Chaluma Tujuba. "Sex Determination in Plants and its Contribution to Genetic Variability." EAS Journal of Biotechnology and Genetics 4, no. 4 (July 29, 2022): 47–54. http://dx.doi.org/10.36349/easjbg.2022.v04i04.002.
Full textAbstract:
Sex determination is a process that leads to the physical separation of male and female gamete-producing structures to different individuals of a species. Sexual reproduction is an ancient feature of eukaryote life, yet the sexes as we currently recognize them are relative late comers in the evolution of sex. Sex determination systems in plants have evolved many times from hermaphroditic ancestors (including monoecious plants with separate male and female flowers on the same individual),and sex chromosome systems have arisen several times in flowering plant evolution. Sex chromosome evolution is intimately connected with Y chromosome degeneration. Most current understanding of how the distinctive properties of Y chromosomes evolved comes from theoretical work on the evolution of genomic regions with low recombination. The identification of sex chromosomes in plants is problematic because most of them do not differ morphologically from autosomes or from one another. For example in some species, such as Actinidia deliciosa var. deliciosa, X and Y chromosomes are too small to support observations of their distinguishing characteristics.) In the majority of plants, male and female organs are formed and developed simultaneously, but only up to a point when the growth of either set of sex organs is inhibited. Inhibition of sexual development can vary in character so that in most cases, sexual development is inhibited by the absence of cell division. In many species of bryophytes, heterothallism (unisexuality) has been correlated with the presence of sex chromosomes. Although the extent of heterothallism and sex chromosomes in the bryophytes has not been assessed systematically, this is the only known group of homosporous plants that uses sex chromosomes in sex determination. To date, studies of bryophyte sex determination have focused on the heterothallic liverwort Marchantia polymorpha. Many dioecious species, including those with well-developed sex chromosomes, ........
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Zhang, Rui, Linda Amah, and Anthony C. Fiumera. "Autosomal variation for male body size and sperm competition phenotypes is uncorrelated in Drosophila melanogaster." Biology Letters 4, no. 5 (June 24, 2008): 500–503. http://dx.doi.org/10.1098/rsbl.2008.0283.
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Correlations between male body size and phenotypes impacting post-copulatory sexual selection are commonly observed during the manipulation of male body size by environmental rearing conditions. Here, we control for environmental influences and test for genetic correlations between natural variation in male body size and phenotypes affecting post-copulatory sexual selection in Drosophila melanogaster . Dry weights of virgin males from 90 second-chromosome and 88 third-chromosome substitution lines were measured. Highly significant line effects ( p <0.001) documented a genetic basis to variation in male body size. No significant correlations were identified between male body size and the components of sperm competitive ability. These results suggest that natural autosomal variation for male body size has little impact on post-copulatory sexual selection. If genetic correlations exist between male body size and post-copulatory sexual selection then variation in the sex chromosomes are likely candidates, as might be expected if sexually antagonistic coevolution was responsible.
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Lichilín, Nicolás, Athimed El Taher, and Astrid Böhne. "Sex-biased gene expression and recent sex chromosome turnover." Philosophical Transactions of the Royal Society B: Biological Sciences 376, no. 1833 (July 26, 2021): 20200107. http://dx.doi.org/10.1098/rstb.2020.0107.
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Cichlids are well known for their propensity to radiate generating arrays of morphologically and ecologically diverse species in short evolutionary time. Following this rapid evolutionary pace, cichlids show high rates of sex chromosome turnover. We here studied the evolution of sex-biased gene (SBG) expression in 14 recently diverged taxa of the Lake Tanganyika Tropheini cichlids, which show different XY sex chromosomes. Across species, sex chromosome sequence divergence predates divergence in expression between the sexes. Only one sex chromosome, the oldest, showed signs of demasculinization in gene expression and potentially contribution to the resolution of sexual conflict. SBGs in general showed high rates of turnovers and evolved mostly under drift. Sexual selection did not shape the rapid evolutionary changes of SBGs. Male-biased genes evolved faster than female-biased genes, which seem to be under more phylogenetic constraint. We found a relationship between the degree of sex bias and sequence evolution driven by sequence differences among the sexes. Consistent with other species, strong sex bias towards sex-limited expression contributes to resolving sexual conflict in cichlids. This article is part of the theme issue ‘Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part II)’.
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SAWAMURA, KYOICHI, YOSHIHIKO TOMIMURA, HAJIME SATO, HIROKAZU YAMADA, MUNEO MATSUDA, and YUZURU OGUMA. "Establishing interspecific mosaic genome lines between Drosophila ananassae and Drosophila pallidosa by means of parthenogenesis." Genetical Research 88, no. 1 (August 2006): 1–11. http://dx.doi.org/10.1017/s0016672306008299.
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Strong sexual isolation exists between the closely related species Drosophila ananassae and D. pallidosa, but there is no obvious post-mating isolation; both sexes of the hybrids and their descendants appear to be completely viable and fertile. Strains exhibiting parthenogenesis have been derived from wild populations of both species. We intercrossed such strains and established iso-female lines after the second generation of parthenogenesis. These lines are clones, carrying homozygous chromosomes that are interspecific recombinants. We established 266 such isogenic lines and determined their genetic constitution by using chromosomal and molecular markers. Strong pseudo-linkage was seen between loci on the left arm of chromosome 2 and on the right arm of chromosome 3; the frequency of inheriting the two chromosome regions from the same species was significantly larger than expected. One possible cause of pseudo-linkage is female meiotic bias, so that chromosomes of the same species origin tend to be distributed to the same gamete. But this possibility is ruled out; backcross analysis indicated that the two chromosome regions segregated independently in female hybrids. The remaining possibility is elimination of low-fitness flies carrying the two chromosome regions from different species. Thus, genetic incompatibility was detected in the species pair for which no hybrid breakdown had previously been indicated. The ‘interspecific mosaic genome’ lines reported here will be useful for future research to identify genes involved in speciation and phenotypic evolution.
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Maxson, Stephen C. "Sexual selection and the Y chromosome." Trends in Ecology & Evolution 14, no. 6 (June 1999): 236. http://dx.doi.org/10.1016/s0169-5347(99)01623-7.
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Zolan, M. E., N. K. Heyler, and N. Y. Stassen. "Inheritance of chromosome-length polymorphisms in Coprinus cinereus." Genetics 137, no. 1 (May 1, 1994): 87–94. http://dx.doi.org/10.1093/genetics/137.1.87.
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Abstract We have investigated the inheritance of chromosome-length polymorphisms in the basidiomycete Coprinus cinereus. The electrophoretic karyotypes of interfertile strains of C. cinereus are strikingly different, and crosses between strains with different karyotypes yield progeny with chromosomes of new sizes. Repeated backcrossing of a mutant to one parent often stabilizes the mutant chromosome at a unique size; this then becomes a chromosome-length polymorphism marker for that mutant gene. A comparison of mutant strains, their wild-type progenitor, and backcrossed strains revealed that these marker chromosomes are not caused by the initial mutagenic treatment and are found only in progeny of crosses between strains with polymorphic chromosomes. Thus, they are most likely formed by meiotic recombination. For the rad12 gene, the marker chromosome can further recombine to become the size of the homolog of the backcross parent. For the rad3 gene, both ectopic and homologous recombination events are likely involved in the generation of the marker chromosomes. As predicted by a recombination model, a cross to a new wild-type parent can change the size of a mutant marker chromosome. Therefore, changes in chromosome length are a common and prominent feature of the genome of this sexual fungus, and a variety of karyotypes is tolerated by the organism.
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Vašut, Radim J., Kitty Vijverberg, Peter J. van Dijk, and Hans de Jong. "Fluorescent in situ hybridization shows DIPLOSPOROUS located on one of the NOR chromosomes in apomictic dandelions (Taraxacum) in the absence of a large hemizygous chromosomal region." Genome 57, no. 11/12 (November 2014): 609–20. http://dx.doi.org/10.1139/gen-2014-0143.
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Apomixis in dandelions (Taraxacum: Asteraceae) is encoded by two unlinked dominant loci and a third yet undefined genetic factor: diplosporous omission of meiosis (DIPLOSPOROUS, DIP), parthenogenetic embryo development (PARTHENOGENESIS, PAR), and autonomous endosperm formation, respectively. In this study, we determined the chromosomal position of the DIP locus in Taraxacum by using fluorescent in situ hybridization (FISH) with bacterial artificial chromosomes (BACs) that genetically map within 1.2–0.2 cM of DIP. The BACs showed dispersed fluorescent signals, except for S4-BAC 83 that displayed strong unique signals as well. Under stringent blocking of repeats by C0t-DNA fragments, only a few fluorescent foci restricted to defined chromosome regions remained, including one on the nucleolus organizer region (NOR) chromosomes that contains the 45S rDNAs. FISH with S4-BAC 83 alone and optimal blocking showed discrete foci in the middle of the long arm of one of the NOR chromosomes only in triploid and tetraploid diplosporous dandelions, while signals in sexual diploids were lacking. This agrees with the genetic model of a single dose, dominant DIP allele, absent in sexuals. The length of the DIP region is estimated to cover a region of 1–10 Mb. FISH in various accessions of Taraxacum and the apomictic sister species Chondrilla juncea, confirmed the chromosomal position of DIP within Taraxacum but not outside the genus. Our results endorse that, compared to other model apomictic species, expressing either diplospory or apospory, the genome of Taraxacum shows a more similar and less diverged chromosome structure at the DIP locus. The different levels of allele sequence divergence at apomeiosis loci may reflect different terms of asexual reproduction. The association of apomeiosis loci with repetitiveness, dispersed repeats, and retrotransposons commonly observed in apomictic species may imply a functional role of these shared features in apomictic reproduction, as is discussed.
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Bista, Basanta, and Nicole Valenzuela. "Turtle Insights into the Evolution of the Reptilian Karyotype and the Genomic Architecture of Sex Determination." Genes 11, no. 4 (April 11, 2020): 416. http://dx.doi.org/10.3390/genes11040416.
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Sex chromosome evolution remains an evolutionary puzzle despite its importance in understanding sexual development and genome evolution. The seemingly random distribution of sex-determining systems in reptiles offers a unique opportunity to study sex chromosome evolution not afforded by mammals or birds. These reptilian systems derive from multiple transitions in sex determination, some independent, some convergent, that lead to the birth and death of sex chromosomes in various lineages. Here we focus on turtles, an emerging model group with growing genomic resources. We review karyotypic changes that accompanied the evolution of chromosomal systems of genotypic sex determination (GSD) in chelonians from systems under the control of environmental temperature (TSD). These transitions gave rise to 31 GSD species identified thus far (out of 101 turtles with known sex determination), 27 with a characterized sex chromosome system (13 of those karyotypically). These sex chromosomes are varied in terms of the ancestral autosome they co-opted and thus in their homology, as well as in their size (some are macro-, some are micro-chromosomes), heterogamety (some are XX/XY, some ZZ/ZW), dimorphism (some are virtually homomorphic, some heteromorphic with larger-X, larger W, or smaller-Y), age (the oldest system could be ~195 My old and the youngest < 25 My old). Combined, all data indicate that turtles follow some tenets of classic theoretical models of sex chromosome evolution while countering others. Finally, although the study of dosage compensation and molecular divergence of turtle sex chromosomes has lagged behind research on other aspects of their evolution, this gap is rapidly decreasing with the acceleration of ongoing research and growing genomic resources in this group.
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Hodges, Craig A., Renée LeMaire-Adkins, and Patricia A. Hunt. "Coordinating the segregation of sister chromatids during the first meiotic division: evidence for sexual dimorphism." Journal of Cell Science 114, no. 13 (July 1, 2001): 2417–26. http://dx.doi.org/10.1242/jcs.114.13.2417.
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Errors during the first meiotic division are common in our species, but virtually all occur during female meiosis. The reason why oogenesis is more error prone than spermatogenesis remains unknown. Normal segregation of homologous chromosomes at the first meiotic division (MI) requires coordinated behavior of the sister chromatids of each homolog. Failure of sister kinetochores to act cooperatively at MI, or precocious sister chromatid segregation (PSCS), has been postulated to be a major contributor to human nondisjunction. To investigate the factors that influence PSCS we utilized the XO mouse, since the chromatids of the single X chromosome frequently segregate at MI, and the propensity for PSCS is influenced by genetic background. Our studies demonstrate that the strain-specific differences in PSCS are due to the actions of an autosomal trans-acting factor or factors. Since components of the synaptonemal complex are thought to play a role in centromere cohesion and kinetochore orientation, we evaluated the behavior of the X chromosome at prophase to determine if this factor influenced the propensity of the chromosome for self-synapsis. We were unable to directly correlate synaptic differences with subsequent segregation behavior. However, unexpectedly, we uncovered a sexual dimorphism that may partially explain sex-specific differences in the fidelity of meiotic chromosome segregation. Specifically, in the male remnants of the synaptonemal complex remain associated with the centromeres until anaphase of the second meiotic division (MII), whereas in the female, all traces of synaptonemal complex (SC) protein components are lost from the chromosomes before the onset of the first meiotic division. This finding suggests a sex-specific difference in the components used to correctly segregate chromosomes during meiosis, and may provide a reason for the high error frequency during female meiosis.
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Sunnucks, Paul, Phillip R. England, Andrea C. Taylor, and Dinah F. Hales. "Microsatellite and Chromosome Evolution of Parthenogenetic Sitobion Aphids in Australia." Genetics 144, no. 2 (October 1, 1996): 747–56. http://dx.doi.org/10.1093/genetics/144.2.747.
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Abstract Single-locus microsatellite variation correlated perfectly with chromosome number in Sitobion miscanthi aphids. The microsatellites were highly heterozygous, with up to 10 alleles per locus in this species. Despite this considerable allelic variation, only seven different S. miscanthi genotypes were discovered in 555 individuals collected from a wide range of locations, hosts and sampling periods. Relatedness between genotypes suggests only two successful colonizations of Australia. There was no evidence for genetic recombination in 555 S. miscanthi so the occurrence of recent sexual reproduction must be near zero. Thus diversification is by mutation and chromosomal rearrangement alone. Since the aphids showed no sexual recombination, microsatellites can mutate without meiosis. Five of seven microsatellite differences were a single repeat unit, and one larger jump is likely. The minimum numbers of changes between karyotypes corresponded roughly one-to-one with microsatellite allele changes, which suggests very rapid chromosomal evolution. A chromosomal fission occurred in a cultured line, and a previously unknown chromosomal race was detected. All 121 diverse S. near fragariae were heterozygous but revealed only one genotype. This species too must have a low rate of sexual reproduction and few colonizations of Australia.
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Abraham, Alicia Leonor Basso. "Autosexing strains to control populations of fruit flies (DIPTERA: Tephritidae): why do they fail to succeed?" Journal of Applied Biotechnology & Bioengineering 8, no. 5 (October 14, 2021): 139–43. http://dx.doi.org/10.15406/jabb.2021.08.00267.
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The development of a unique genetic sexing strain to control fruit fly populations has repetedly failed. But why do they fail to succed? We previously demonstrated in Certitis capitata (Wied.) that the autosexing mechanism must be developed on the germplasm of the population to be controled. The present integrative study addresses the causes for the lack of success, thus studying: 1- compatibility tests between Anastrepha fraterculus (Wied.) germplasms from different geographic origins; 2- the genotype by environment interaction component of phenotypic variation in A. fraterculus and 3- essential knowledge on polymorphisms of the Y-chromosome carrying the marker linked to male sex. Our hypothesis: a- chromosomal and morphological variants are associated to different argentinian geographic populations of C. capitata; b- chromosomal variants are not randomly distributed in A. fraterculus populations. We sampled guava fruits during 30 years to recover larvae and adult flies from both species, in order to study the chromosomal pattern of larvae from wild populations and derived strains. Banding patterns were obtained with routine and molecular cytogenetics. Sexual chromosome variants were associated to different strains. Analysis showed ten sexual chromosome variants in A. fraterculus. In C. capitata we found sexual chromosome polymorphisms for the X as well as for the Y. Our results -throughout the years- show the necessity of performing periodically genetic samplings of the populations to be treated in order to detect new mutations affecting mating beahaviour between laboratory and wild populations or lack of compatibiliy when applying the sterile male technique. The study of genotype by environment interaction parameter is mandatory to identify the right germplasms on which to develop the autosexing mechanism in order to successfully control populations of both fruit flies species
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Pearse, Devon E., Nicola J. Barson, Torfinn Nome, Guangtu Gao, Matthew A. Campbell, Alicia Abadía-Cardoso, Eric C. Anderson, et al. "Sex-dependent dominance maintains migration supergene in rainbow trout." Nature Ecology & Evolution 3, no. 12 (November 25, 2019): 1731–42. http://dx.doi.org/10.1038/s41559-019-1044-6.
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AbstractMales and females often differ in their fitness optima for shared traits that have a shared genetic basis, leading to sexual conflict. Morphologically differentiated sex chromosomes can resolve this conflict and protect sexually antagonistic variation, but they accumulate deleterious mutations. However, how sexual conflict is resolved in species that lack differentiated sex chromosomes is largely unknown. Here we present a chromosome-anchored genome assembly for rainbow trout (Oncorhynchus mykiss) and characterize a 55-Mb double-inversion supergene that mediates sex-specific migratory tendency through sex-dependent dominance reversal, an alternative mechanism for resolving sexual conflict. The double inversion contains key photosensory, circadian rhythm, adiposity and sex-related genes and displays a latitudinal frequency cline, indicating environmentally dependent selection. Our results show sex-dependent dominance reversal across a large autosomal supergene, a mechanism for sexual conflict resolution capable of protecting sexually antagonistic variation while avoiding the homozygous lethality and deleterious mutations associated with typical heteromorphic sex chromosomes.
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Liu, Dong, Lang Gui, Yefei Zhu, Cong Xu, Wenzong Zhou, and Mingyou Li. "Chromosome-Level Assembly of Male Opsariichthys bidens Genome Provides Insights into the Regulation of the GnRH Signaling Pathway and Genome Evolution." Biology 11, no. 10 (October 13, 2022): 1500. http://dx.doi.org/10.3390/biology11101500.
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The hook snout carp Opsariichthys bidens is an important farmed fish in East Asia that shows sexual dimorphism in growth, with males growing faster and larger than females. To understand these complex traits and improve molecular breeding, chromosome-level genome assembly of male O. bidens was performed using Illumina, Nanopore, and Hi-C sequencing. The 992.9 Mb genome sequences with a contig N50 of 5.2 Mb were anchored to 38 chromosomes corresponding to male karyotypes. Of 30,922 functionally annotated genes, 97.5% of BUSCO genes were completely detected. Genome evolution analysis showed that the expanded and contracted gene families in the male O. bidens genome were enriched in 76 KEGG pathways, and 78 expanded genes were involved in the GnRH signaling pathway that regulates the synthesis and secretion of luteinizing hormone and glycoprotein hormones, further acting on male growth by inducing growth hormone. Compared to the released female O. bidens genome, the number of annotated genes in males was much higher (23,992). The male chromosome LG06 exhibited over 97% identity with the female GH14/GH38. Male-specific genes were identified for LG06, where structural variation, including deletions and insertions, occurred at a lower rate, suggesting a centric fusion of acrocentric chromosomes GH14 and GH38. The genome-synteny analysis uncovered significant inter-chromosome conservation between male O. bidens and grass carp, the former originating from ancestral chromosome breakage to increase the chromosome number. Our results provide a valuable genetic resource for studying the regulation of sexual dimorphism, sex-determining mechanisms, and molecular-guided breeding of O. bidens.
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Furman, Benjamin L. S., David C. H. Metzger, Iulia Darolti, Alison E. Wright, Benjamin A. Sandkam, Pedro Almeida, Jacelyn J. Shu, and Judith E. Mank. "Sex Chromosome Evolution: So Many Exceptions to the Rules." Genome Biology and Evolution 12, no. 6 (April 21, 2020): 750–63. http://dx.doi.org/10.1093/gbe/evaa081.
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Abstract Genomic analysis of many nonmodel species has uncovered an incredible diversity of sex chromosome systems, making it possible to empirically test the rich body of evolutionary theory that describes each stage of sex chromosome evolution. Classic theory predicts that sex chromosomes originate from a pair of homologous autosomes and recombination between them is suppressed via inversions to resolve sexual conflict. The resulting degradation of the Y chromosome gene content creates the need for dosage compensation in the heterogametic sex. Sex chromosome theory also implies a linear process, starting from sex chromosome origin and progressing to heteromorphism. Despite many convergent genomic patterns exhibited by independently evolved sex chromosome systems, and many case studies supporting these theoretical predictions, emerging data provide numerous interesting exceptions to these long-standing theories, and suggest that the remarkable diversity of sex chromosomes is matched by a similar diversity in their evolution. For example, it is clear that sex chromosome pairs are not always derived from homologous autosomes. In addition, both the cause and the mechanism of recombination suppression between sex chromosome pairs remain unclear, and it may be that the spread of recombination suppression is a more gradual process than previously thought. It is also clear that dosage compensation can be achieved in many ways, and displays a range of efficacy in different systems. Finally, the remarkable turnover of sex chromosomes in many systems, as well as variation in the rate of sex chromosome divergence, suggest that assumptions about the inevitable linearity of sex chromosome evolution are not always empirically supported, and the drivers of the birth–death cycle of sex chromosome evolution remain to be elucidated. Here, we concentrate on how the diversity in sex chromosomes across taxa highlights an equal diversity in each stage of sex chromosome evolution.
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Hollocher, Hope, Chau-Ti Ting, Mao-Lien Wu, and Chug-I. Wu. "Incipient Speciation by Sexual Isolation in Drosophila melanogaster: Extensive Genetic Divergence Without Reinforcement." Genetics 147, no. 3 (November 1, 1997): 1191–201. http://dx.doi.org/10.1093/genetics/147.3.1191.
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The collection of Drosophila melanogaster from Zimbabwe and nearby regions (the Z-type) yield females who would not mate with the cosmopolitan D. melanogaster males (the M-type). To dissect the genetic basis of this sexual isolation, we constructed 16 whole-chromosome substitution lines between two standard Z- and M-lines. The results were as follows: (1) All substitution lines appear normal in viability and fertility in both sexes, indicating no strong postmating isolation. (2) The genes for the behaviors are mapped to all three major chromosomes with the same ranking and comparable magnitude of effects for both sexes: III > II ⪢ X ≥ 0 (III, II and X designate the effects of the three chromosomes). The results suggest less evolution on the X than on autosomes at loci of sexual behavior. (3) The genes for “Z-maleness” are many and somewhat redundant. Whole-chromosome effects for Z-maleness appear nearly additive and show little dominance. (4) In contrast, “Z-femaleness” has less redundancy as partial genotypes never exhibit full phenotypic effects. Epistatic interactions and incomplete dominance can sometimes be detected. (5) The extensive genetic divergence underlying sexual isolation has evolved in the absence of detectable reduction in hybrid fitnesses. Sexual selection has apparently been a driving force of multiple facets of speciation at the nascent stage without reinforcement.
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Hanley, Neil. "Slugs and snails, or sugar and spice?: Sex determination and sexual differentiation." Biochemist 24, no. 2 (April 1, 2002): 12–15. http://dx.doi.org/10.1042/bio02402012.
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Mammalian existence relies upon pregnancy producing either male or female offspring. Under normal circumstances, this ‘polarized’ outcome is determined by the chromosomal constitution of the spermatozoan that successfully fertilizes the ovum -- a Y chromosome acts dominantly to produce a male foetus. This concept of sex chromosome action has been with us for almost a century1. However, understanding the genetic steps between fertilization and the development of male or female appearance proved less forthcoming for a long time. Building upon the landmark experiments of Jost in the 1940s2, the previous decade has witnessed significant advances in the understanding of male and female development3. For the most part, information has arisen either by genetic manipulation of laboratory mice or by careful clinical and molecular genetic analyses of human individuals with sex reversal. In both circumstances, chromosomal constitution (46,XY or 46,XX) fails to correspond to the sexual phenotype (male or female).
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Kusz, Kamila, Maciej Kotecki, Alina Wojda, Maria Szarras-Czapnik, Anna Latos-Bielenska, Alina Warenik-Szymankiewicz, Anna Ruszczynska-Wolska, and Jadwiga Jaruzelska. "Incomplete masculinisation of XX subjects carrying the SRY gene on an inactive X chromosome." Journal of Medical Genetics 36, no. 6 (June 1, 1999): 452–56. http://dx.doi.org/10.1136/jmg.36.6.452.
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46,XX subjects carrying the testis determining SRY gene usually have a completely male phenotype. In this study, five very rare cases of SRY carrying subjects (two XX males and three XX true hermaphrodites) with various degrees of incomplete masculinisation were analysed in order to elucidate the cause of sexual ambiguity despite the presence of the SRY gene. PCR amplification of 20 Y chromosome specific sequences showed the Yp fragment to be much longer in XX males than in true hermaphrodites. FISH analysis combined with RBG banding of metaphase chromosomes of four patients showed that in all three true hermaphrodites and in one XX male the Yp fragment was translocated onto a late replicating inactive X chromosome in over 90% of their blood lymphocytes. However, in a control classical XX male with no ambiguous features, the Yp fragment (significantly shorter than in the XX male with sexual ambiguity and only slightly longer than in XX hermaphrodites) was translocated onto the active X chromosome in over 90% of cells.These studies strongly indicate that inactivation on the X chromosome spreading into a translocated Yp fragment could be the major mechanism causing a sexually ambiguous phenotype in XX (SRY+) subjects.
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MILLER, MARVIN E., and STEPHEN SULKES. "Fire-Setting Behavior in Individuals With Klinefelter Syndrome." Pediatrics 82, no. 1 (July 1, 1988): 115–17. http://dx.doi.org/10.1542/peds.82.1.115.
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Klinefelter syndrome is a sex chromosome disorder with an incidence of approximately two per 1,000 male newborns.1 Eighty percent of individuals with Klinefelter syndrome are 47,XXY, whereas the other 20% have a variant sex chromosomal constitution with additional supernumerary X or Y chromosomes (ie, 48,XXXY, 48XXYY) or are mosaic.2 Individuals with Klinefelter syndrome have small testes which usually cannot produce sperm or normal amounts of testosterone. The results of this are infertility and undermasculinization. Behavioral and psychiatric problems are also common in individuals with Klinefelter syndrome and include personality disorder, reactive depression, schizophrenia, mental deficiency, sexual deviation, criminal behavior, and alcoholism.3
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Castro, Jonathan Pena, Ricardo Shohei Hattori, Túlio Teruo Yoshinaga, Duílio Mazzoni Zerbinato de Andrade Silva, Francisco J. Ruiz-Ruano, Fausto Foresti, Mateus Henrique Santos, Mara Cristina de Almeida, Orlando Moreira-Filho, and Roberto Ferreira Artoni. "Differential Expression of Genes Related to Sexual Determination Can Modify the Reproductive Cycle of Astyanax scabripinnis (Characiformes: Characidae) in B Chromosome Carrier Individuals." Genes 10, no. 11 (November 8, 2019): 909. http://dx.doi.org/10.3390/genes10110909.
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The species complex Astyanax scabripinnis is one of the most studied with respect to origin, distribution, and frequency of B chromosomes, and is considered a model organism for evolutionary studies. Research using population inferences about the occurrence and frequency of the B chromosome shows seasonal variation between sexes, which is associated with the presence of this supernumerary element. We hypothesized that the B chromosome could influence the sex ratio of these animals. Based on this assumption, the present work aimed to investigate if differences exist among levels of gene expression with qRT-PCR of the amh (associated with testicular differentiation) and foxl2a (associated with ovarian differentiation) genes between B-carrier and non-B-carrier individuals. The results showed that for the amh gene, the difference in expression between animals with B chromosomes was not accentuated compared to that in animals without this chromosome. Expression of foxl2a in B-carrier females, however, was reduced by 73.56% compared to females that lacked the B chromosome. Males had no difference in expression of the amh and foxl2a genes between carriers and non-carriers of the B chromosome. Results indicate that the presence of B chromosomes is correlated with the differential expression of sex-associated genes. An analysis of these results integrated with data from other studies on the reproductive cycle in the same species reveals that this difference in expression may be expanding the reproductive cycle of the species.
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Noor, Mohamed A. F., and Jerry A. Coyne. "Genetics of a difference in cuticular hydrocarbons between Drosophila pseudoobscura and D. persimilis." Genetical Research 68, no. 2 (October 1996): 117–23. http://dx.doi.org/10.1017/s0016672300034005.
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SummaryWe identify a fixed species difference in the relative concentrations of the cuticular hydrocarbons 2-methyl hexacosane and 5,9-pentacosadiene in Drosophilapseudoobscura and D. persimilis, and determine its genetic basis. In backcross males, this difference is due to genes on both the X and second chromosomes, while the other two major chromosomes have no effect. In backcross females, only the second chromosome has a significant effect on hydrocarbon phenotype, but dominant genes on the X chromosome could also be involved. These results differ in two respects from previous studies of Drosophila cuticular hydrocarbons: strong epistasis is observed between the chromosomes that producethe hydrocarbon difference in males, and the difference is apparently unrelated to the strong sexual isolation observed between these species.
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González-Rodríguez, María Teresa Alejandra, Sinhue Alejandro Brukman-Jiménez, Idalid Cuero-Quezada, Jorge Román Corona-Rivera, Alfredo Corona-Rivera, Graciela Serafín-Saucedo, Liuba M. Aguirre-Salas, and Lucina Bobadilla-Morales. "Identification of a Small Supernumerary Marker Chromosome in a Turner Syndrome Patient with Karyotype mos 46,X,+mar/45,X." Genes 14, no. 2 (January 18, 2023): 253. http://dx.doi.org/10.3390/genes14020253.
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Turner Syndrome is characterized by a normal X chromosome and the partial or complete absence of a second sexual chromosome. Small supernumerary marker chromosomes are present in 6.6% of these patients. Because of the wide range of Turner syndrome karyotypes, it is difficult to establish a relationship with the phenotype of the patients. We present the case of a female patient with Turner syndrome, insulin resistance, type 2 diabetes, and intellectual disability. The karyotype revealed the presence of mosaicism with a monosomy X cell line and a second line with a small marker chromosome. FISH of two different tissues was used to identify the marker chromosome with probes for X and Y centromeres. Both tissues presented mosaicism for a two X chromosome signal, differing in the percentage of the monosomy X cell percentage. Comparative genomic hybridization with the CytoScanTMHD assay was performed in genomic DNA from peripheral blood, allowing us to determine the size and breakage points of the small marker chromosome. The patient presents a phenotype that combines classic Turner syndrome features and unlikely ones as intellectual disability. The size, implicated genes, and degree of inactivation of the X chromosome influence the broad spectrum of phenotypes resulting from these chromosomes.
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Bonthuis, Paul J., Kimberly H. Cox, and Emilie F. Rissman. "X-chromosome dosage affects male sexual behavior." Hormones and Behavior 61, no. 4 (April 2012): 565–72. http://dx.doi.org/10.1016/j.yhbeh.2012.02.003.
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