Differentiation of Y Chromosome in the X1X1X2X2/X1X2Y Sex Chromosome System of Hoplias malabaricus (Characiformes, Erythrinidae)

2009 ◽  
Vol 127 (1) ◽  
pp. 54-60 ◽  
Author(s):  
R. da Rosa ◽  
A.L. Laforga Vanzela ◽  
M. Rubert ◽  
I.C. Martins-Santos ◽  
L. Giuliano-Caetano
Keyword(s):  
Y Chromosome ◽  
Sex Chromosome ◽  
Hoplias Malabaricus ◽  
Sex Chromosome System

scholarly journals A new sympatric region for distinct karyotypic forms of Hoplias malabaricus (Pisces, Erythrinidae)

2006 ◽  
Vol 66 (1b) ◽  
pp. 205-210 ◽  
Author(s):  
G. G. Born ◽  
L. A. C. Bertollo
Keyword(s):  
Sex Difference ◽  
Sex Chromosomes ◽  
Diploid Number ◽  
Sex Chromosome ◽  
Minas Gerais ◽  
Female Specimen ◽  
Male Specimen ◽  
Hoplias Malabaricus ◽  
Sex Chromosome System ◽  
Sympatric Cytotypes

Specimens of Hoplias malabaricus from Lagoa Carioca, an isolated lake of the Rio Doce State Park (state of Minas Gerais, Brazil), were cytogenetically studied. The diploid number was found to be constant, i.e., 2n = 42 chromosomes, although two karyotypic forms were found: karyotype A, characterized by 22M + 20SM chromosomes, observed only in a male specimen, and karyotype B, characterized by 24M + 16SM + 2ST and 24M + 17SM + 1ST chromosomes in female and male specimens, respectively. This sex difference found in karyotype B is related to an XX/XY sex chromosome system. Another female specimen of H. malabaricus, also carrying karyotype A, had previously been found in the same lake. The available data indicate that two sympatric cytotypes of H. malabaricus exist in the Lagoa Carioca, with cytotype A occurring at a lower frequency and differing from cytotype B by undifferentiated sex chromosomes.

From brain determination to testis determination: evolution of the mammalian sex-determining gene

2001 ◽  
Vol 13 (8) ◽  
pp. 665 ◽  
Author(s):  
Jennifer A. Marshall Graves
Keyword(s):  
Y Chromosome ◽  
Sex Chromosome ◽  
Critical Role ◽  
Dominant Gene ◽  
Comparative Gene Mapping ◽  
Good Account ◽  
Mole Vole ◽  
Sex Chromosome System ◽  
Testis Determination ◽  
Autosome Pair

In mammals, sex is determined by an XY male:XX female sex chromosome system in which a male-dominant gene on the Y chromosome (SRY) determines testis formation. Sex chromosomes evolved from an ordinary autosome pair as the Y chromosome was progressively degraded. The Y chromosome has lost nearly all of its 1500 original genes, and those that survived did so because they evolved a critical role in male determination or differentiation. SRY is typical of Y-borne genes. Comparative gene mapping and sequencing shows that SRY arose quite recently as a degraded version of the SOX3 gene on the X chromosome. SOX3 is expressed predominantly in brain, and so is more likely to be a brain-determining than a testis-determining gene. The male-dominant action of SRY may be an illusion, as its structure suggests that it works by interfering with the action of a related gene, which in turn inhibits testis development. This hypothesis can give a good account of how a brain-determining gene acquired a role in testis determination via differential dosage of SOX3. SRY has no central role in sex determination and it can be replaced as a trigger and lost, as have many other Y-borne genes in recent evolutionary history. The absence of SRY in two species of the mole vole (Ellobius) suggests that its useful life is already running out.

scholarly journals Extreme heterogeneity in sex chromosome differentiation and dosage compensation in livebearers

2019 ◽  
Author(s):  
Iulia Darolti ◽  
Alison E. Wright ◽  
Benjamin A. Sandkam ◽  
Jake Morris ◽  
Natasha I. Bloch ◽  
...  
Keyword(s):  
Y Chromosome ◽  
Dosage Compensation ◽  
Sex Chromosomes ◽  
Poecilia Reticulata ◽  
Sex Chromosome ◽  
Sequencing Data ◽  
Chromosome Differentiation ◽  
Shared Ancestry ◽  
Sex Chromosome System ◽  
Suppressed Recombination

ABSTRACTOnce recombination is halted between the X and Y chromosome, sex chromosomes begin to differentiate and transition to heteromorphism. While there is a remarkable variation across clades in the degree of sex chromosome divergence, far less is known about variation in sex chromosome differentiation within clades. Here, we combined whole genome and transcriptome sequencing data to characterise the structure and conservation of sex chromosome systems across Poeciliidae, the livebearing clade that includes guppies. We found that the Poecilia reticulata XY system is much older than previously thought, being shared not only with its sister species, Poecilia wingei, but also with Poecilia picta, which diverged 30 mya. Despite the shared ancestry, we uncovered an extreme heterogeneity across these species in the proportion of the sex chromosome with suppressed recombination, and the degree of Y chromosome decay. The sex chromosomes in P. reticulata are largely homomorphic, with recombination persisting over a substantial fraction. However, the sex chromosomes in P. picta are completely non-recombining and strikingly heteromorphic. ln addition to being highly divergent, the sex chromosome system in P. picta includes a neo-sex chromosome, the result of a fusion between the ancestral sex chromosome and part of chromosome 7. Remarkably, the profound degradation of the ancestral Y chromosome in P. picta is counterbalanced by the evolution of complete dosage compensation in this species, the first such documented case in teleost fish. Our results offer important insight into the initial stages of sex chromosome evolution and dosage compensation.

scholarly journals Guppy Y Chromosome Integrity Maintained by Incomplete Recombination Suppression

2020 ◽  
Vol 12 (6) ◽  
pp. 965-977 ◽  
Author(s):  
Iulia Darolti ◽  
Alison E Wright ◽  
Judith E Mank
Keyword(s):  
Y Chromosome ◽  
X Chromosome ◽  
Sex Chromosomes ◽  
Poecilia Reticulata ◽  
Sex Chromosome ◽  
Rna Seq ◽  
Recombination Suppression ◽  
Sex Chromosome System ◽  
Chromosome Integrity ◽  
Heterogametic Sex

Abstract The loss of recombination triggers divergence between the sex chromosomes and promotes degeneration of the sex-limited chromosome. Several livebearers within the genus Poecilia share a male-heterogametic sex chromosome system that is roughly 20 Myr old, with extreme variation in the degree of Y chromosome divergence. In Poecilia picta, the Y is highly degenerate and associated with complete X chromosome dosage compensation. In contrast, although recombination is restricted across almost the entire length of the sex chromosomes in Poecilia reticulata and Poecilia wingei, divergence between the X chromosome and the Y chromosome is very low. This clade therefore offers a unique opportunity to study the forces that accelerate or hinder sex chromosome divergence. We used RNA-seq data from multiple families of both P. reticulata and P. wingei, the species with low levels of sex chromosome divergence, to differentiate X and Y coding sequences based on sex-limited SNP inheritance. Phylogenetic tree analyses reveal that occasional recombination has persisted between the sex chromosomes for much of their length, as X- and Y-linked sequences cluster by species instead of by gametolog. This incomplete recombination suppression maintains the extensive homomorphy observed in these systems. In addition, we see differences between the previously identified strata in the phylogenetic clustering of X–Y orthologs, with those that cluster by chromosome located in the older stratum, the region previously associated with the sex-determining locus. However, recombination arrest appears to have expanded throughout the sex chromosomes more gradually instead of through a stepwise process associated with inversions.

scholarly journals A Selective Sweep Associated With a Recent Gene Transposition in Drosophila miranda

Genetics ◽  
2000 ◽  
Vol 156 (4) ◽  
pp. 1753-1763 ◽  
Author(s):  
Soojin Yi ◽  
Brian Charlesworth
Keyword(s):  
Y Chromosome ◽  
X Chromosome ◽  
Sequence Variation ◽  
Selective Sweep ◽  
Sex Chromosome ◽  
Selective Advantage ◽  
Chromosome Fusion ◽  
Gene Transposition ◽  
Sex Chromosome System ◽  
Male Specific

Abstract In Drosophila miranda, a chromosome fusion between the Y chromosome and the autosome corresponding to Muller’s element C has created a new sex chromosome system. The chromosome attached to the ancestral Y chromosome is transmitted paternally and hence is not exposed to crossing over. This chromosome, conventionally called the neo-Y, and the homologous neo-X chromosome display many properties of evolving sex chromosomes. We report here the transposition of the exuperantia1 (exu1) locus from a neo-sex chromosome to the ancestral X chromosome of D. miranda. Exu1 is known to have several critical developmental functions, including a male-specific role in spermatogenesis. The ancestral location of exu1 is conserved in the sibling species of D. miranda, as well as in a more distantly related species. The transposition of exu1 can be interpreted as an adaptive fixation, driven by a selective advantage conferred by its effect on dosage compensation. This explanation is supported by the pattern of within-species sequence variation at exu1 and the nearby exu2 locus. The implications of this phenomenon for genome evolution are discussed.

The polytene chromosomes of Simulium furculatum (Shewell) (Diptera: Simuliidae)

Genome ◽  
1989 ◽  
Vol 32 (4) ◽  
pp. 522-530
Author(s):  
Fiona F. Hunter
Keyword(s):  
Y Chromosome ◽  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Polytene Chromosomes ◽  
Species Group ◽  
Western Canada ◽  
Black Flies ◽  
X Chromosomes ◽  
Group A ◽  
Sex Chromosome System

To test whether Simulium furculatum (Shewell) belongs to the Simulium vernum (Macquart) species-group, a comparison was made of the polytene chromosomes of S. furculatum and the S. vernum "Knebworth" standard. Only two chromosome arms (of six) could be completely analysed. It is argued that S. furculatum does not belong to the S. vernum species-group. A complex sex-chromosome system (X1, X2, Y1) is found in both eastern and western Canada. Phylogenetically, the single Y chromosome is intermediate between the two X chromosomes. Intraspecific inversion polymorphisms, which serve to differentiate eastern from western populations, are also identified. Only one sibling is indicated.Key words: black flies, Simulium furculatum, Simulium vernum, cytotaxonomy, polytene chromosomes, sex chromosomes.

Genomic Organization of Repetitive DNAs and Differentiation of an XX/XY Sex Chromosome System in the Amazonian Puffer Fish, Colomesus asellus (Tetraodontiformes)

2017 ◽  
Vol 153 (2) ◽  
pp. 96-104 ◽  
Author(s):  
Patrik F. Viana ◽  
Tariq Ezaz ◽  
Leandro Marajó ◽  
Milena Ferreira ◽  
Jansen Zuanon ◽  
...  
Keyword(s):  
Y Chromosome ◽  
Sex Chromosome ◽  
First Record ◽  
Nucleolus Organizer ◽  
X Chromosomes ◽  
Nucleolus Organizer Regions ◽  
Rdna Sites ◽  
Puffer Fish ◽  
Specific Amplification ◽  
Sex Chromosome System

The genus Colomesus is the sole representative of the family Tetraodontidae in the Amazon region. Here, Colomesus asellus was analyzed using conventional and molecular cytogenetic protocols. Its diploid chromosome number is 2n = 46 with 12 meta-, 10 submeta-, 16 subtelo-, and 8 acrocentric chromosomes and a fundamental number of FN = 84. An XX/XY sex chromosome system was identified. Mapping of 18S rDNA correlated with the nucleolus organizer regions (Ag-NORs) in the short arms of the 2 X chromosomes in females and in the Y chromosome in males. C-banding revealed heterochromatin in the centromeric regions of all chromosomes, except for pair 3. Prominent sex chromosome-specific heterochromatin amplification was observed, covering the short arms of the Y chromosome almost entirely. FISH with telomeric and tropomyosin (tpm1) sequences, respectively, revealed terminal signals in all chromosomes. The analysis of extended DNA fibers confirmed the colocalization and the interspersed pattern of the telomeric and tpm1 sequences. Thus, this study highlights the remarkable evolutionary dynamism presented by the Amazonian puffer fish regarding the differentiation of a heteromorphic XY sex chromosome system and a particular sex-specific amplification of rDNA sites. This is the first record of such an association in the Tetraodontidae family.

scholarly journals First cytogenetic information on four checkered beetles (Coleoptera, Cleridae)

2020 ◽  
Vol 14 (4) ◽  
pp. 541-547
Author(s):  
Atılay Yağmur Okutaner
Keyword(s):  
Chromosome Number ◽  
Y Chromosome ◽  
Chromosome Numbers ◽  
Sex Chromosome ◽  
Evolutionary Process ◽  
Sex Chromosome System ◽  
First Time

The karyotypes of four species of Cleridae (Coleoptera): Trichodes favarius (Illiger, 1802), Trichodes quadriguttatus Adams, 1817, Trichodes reichei (Mulsant et Rey, 1863), and Tilloidea transversalis (Charpentier, 1825) were reported for the first time with this study. The chromosome numbers of these four species were determined as 2n = 18, sex chromosome system Xyp, and all chromosomes were metacentric (the except y chromosome). Together with this study, the chromosome data of only 17 species are available in this family. It is remarkable that all of them display the same chromosome number and similar karyotypes. This may make the effect of karyotypical features important in interpreting the evolutionary process of Cleridae.

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