Heteromorphic sex chromosomes in the Australian frog Crinia bilingua (Anura: Myobatrachidae)

Genome ◽  
1991 ◽  
Vol 34 (3) ◽  
pp. 334-337 ◽  
Author(s):  
M. J. Mahony
Keyword(s):  
Sex Chromosomes ◽  
Early Stage ◽  
Proximal Region ◽  
Z Chromosome ◽  
W Chromosome ◽  
Cytological Evidence ◽  
Nucleolar Organiser ◽  
Organiser Region ◽  
Nucleolar Organiser Region ◽  
Heteromorphic Sex Chromosomes

The karyotype of Crinia bilingua was examined and analysed with standard staining, C-banding, and silver-staining. Heteromorphic sex chromosomes of the ZW ♂/ZZ ♀ type were observed. The larger W chromosome is submetacentric and the smaller Z chromosome is acrocentric. The centromere and proximal region of the short arm of the W chromosome consist of constitutive heterochromatin (C-band region), and beyond this is a small euchromatic terminal region. The centromere of the Z chromosome did not C-band. The long arms of the Z and W chromosomes are euchromatic and equal in length. The nucleolar organiser region occurs terminally on the long arm of both the Z and W chromosomes, and there is no cytological evidence for inactivity of the nucleolar organiser region on the W chromosome. These features indicate an early stage in the evolution of heteromorphic sex chromosomes.Key words: heteromorphic sex chromosomes, frog, Crinia bilingua.

scholarly journals Genetic sex determination and sex-specific lifespan in tetrapods – evidence of a toxic Y effect

2020 ◽  
Author(s):  
Zahida Sultanova ◽  
Philip A. Downing ◽  
Pau Carazo
Keyword(s):  
Sex Chromosomes ◽  
Alternative Hypothesis ◽  
Z Chromosome ◽  
W Chromosome ◽  
Deleterious Mutations ◽  
Recessive Mutations ◽  
Y Chromosomes ◽  
Heterogametic Sex ◽  
Taxonomic Patterns

ABSTRACTSex-specific lifespans are ubiquitous across the tree of life and exhibit broad taxonomic patterns that remain a puzzle, such as males living longer than females in birds and vice versa in mammals. The prevailing “unguarded-X” hypothesis (UXh) explains this by differential expression of recessive mutations in the X/Z chromosome of the heterogametic sex (e.g., females in birds and males in mammals), but has only received indirect support to date. An alternative hypothesis is that the accumulation of deleterious mutations and repetitive elements on the Y/W chromosome might lower the survival of the heterogametic sex (“toxic Y” hypothesis). Here, we report lower survival of the heterogametic relative to the homogametic sex across 138 species of birds, mammals, reptiles and amphibians, as expected if sex chromosomes shape sex-specific lifespans. We then analysed bird and mammal karyotypes and found that the relative sizes of the X and Z chromosomes are not associated with sex-specific lifespans, contrary to UXh predictions. In contrast, we found that Y size correlates negatively with male survival in mammals, where toxic Y effects are expected to be particularly strong. This suggests that small Y chromosomes benefit male lifespans. Our results confirm the role of sex chromosomes in explaining sex differences in lifespan, but indicate that, at least in mammals, this is better explained by “toxic Y” rather than UXh effects.

scholarly journals Chromosomal Spreading of Microsatellites and (TTAGGG)n Sequences in the Characidium zebra and C. gomesi Genomes (Characiformes: Crenuchidae)

2016 ◽  
Vol 149 (3) ◽  
pp. 182-190 ◽  
Author(s):  
Marcela B. Pucci ◽  
Patricia Barbosa ◽  
Viviane Nogaroto ◽  
Mara C. Almeida ◽  
Roberto F. Artoni ◽  
...  
Keyword(s):  
Repetitive Dna ◽  
Sex Chromosomes ◽  
Dna Sequences ◽  
Tandem Repeats ◽  
Additional Data ◽  
Sex Chromosome ◽  
Binding Motif ◽  
W Chromosome ◽  
Repeat Sequences ◽  
Heteromorphic Sex Chromosomes

Sex chromosome evolution involves the accumulation of repeat sequences such as multigenic families, noncoding repetitive DNA (satellite, minisatellite, and microsatellite), and mobile elements such as transposons and retrotransposons. Most species of Characidium exhibit heteromorphic ZZ/ZW sex chromosomes; the W is characterized by an intense accumulation of repetitive DNA including dispersed satellite DNA sequences and transposable elements. The aim of this study was to analyze the distribution pattern of 18 different tandem repeats, including (GATA)n and (TTAGGG)n, in the genomes of C. zebra and C. gomesi, especially in the C. gomesi W chromosome. In the C. gomesi W chromosome, weak signals were seen for (CAA)10, (CAC)10, (CAT)10, (CGG)10, (GAC)10, and (CA)15 probes. (GA)15 and (TA)15 hybridized to the autosomes but not to the W chromosome. The (GATA)n probe hybridized to the short arms of the W chromosome as well as the (CG)15 probe. The (GATA)n repeat is known to be a protein-binding motif. GATA-binding proteins are necessary for the decondensation of heterochromatic regions that hold coding genes, especially in some heteromorphic sex chromosomes that may keep genes related to oocyte development. The (TAA)10 repeat is accumulated in the entire W chromosome, and this microsatellite accumulation is probably involved in the sex chromosome differentiation process and crossover suppression in C. gomesi. These additional data on the W chromosome DNA composition help to explain the evolution of sex chromosomes in Characidium.

scholarly journals Argyrophilic nucleolar organiser region counts and prognosis in pharyngeal carcinoma

1991 ◽  
Vol 64 (2) ◽  
pp. 327-332 ◽  
Author(s):  
A Pich ◽  
P Pisani ◽  
M Kzengli ◽  
N Cappello ◽  
R Navone
Keyword(s):  
Nucleolar Organiser ◽  
Organiser Region ◽  
Nucleolar Organiser Region ◽  
Pharyngeal Carcinoma

scholarly journals 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 ◽  
2020 ◽  
Vol 16 (11) ◽  
pp. e1009121
Author(s):  
Benjamin L. S. Furman ◽  
Caroline M. S. Cauret ◽  
Martin Knytl ◽  
Xue-Ying Song ◽  
Tharindu Premachandra ◽  
...  
Keyword(s):  
Sex Differences ◽  
Y Chromosome ◽  
Sex Chromosomes ◽  
Sexual Differentiation ◽  
Sex Chromosome ◽  
Xenopus Tropicalis ◽  
Z Chromosome ◽  
W Chromosome ◽  
Recombination Suppression ◽  
Determining Factor

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.

scholarly journals Evolutionary Variability of W-Linked Repetitive Content in Lacertid Lizards

Genes ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 531
Author(s):  
Grzegorz Suwala ◽  
Marie Altmanová ◽  
Sofia Mazzoleni ◽  
Emmanouela Karameta ◽  
Panayiotis Pafilis ◽  
...  
Keyword(s):  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Phylogenetic Signal ◽  
Z Chromosome ◽  
Specific Gene ◽  
W Chromosome ◽  
Squamate Reptiles ◽  
Lacertid Lizards ◽  
Species Specific

Lacertid lizards are a widely radiated group of squamate reptiles with long-term stable ZZ/ZW sex chromosomes. Despite their family-wide homology of Z-specific gene content, previous cytogenetic studies revealed significant variability in the size, morphology, and heterochromatin distribution of their W chromosome. However, there is little evidence about the accumulation and distribution of repetitive content on lacertid chromosomes, especially on their W chromosome. In order to expand our knowledge of the evolution of sex chromosome repetitive content, we examined the topology of telomeric and microsatellite motifs that tend to often accumulate on the sex chromosomes of reptiles in the karyotypes of 15 species of lacertids by fluorescence in situ hybridization (FISH). The topology of the above-mentioned motifs was compared to the pattern of heterochromatin distribution, as revealed by C-banding. Our results show that the topologies of the examined motifs on the W chromosome do not seem to follow a strong phylogenetic signal, indicating independent and species-specific accumulations. In addition, the degeneration of the W chromosome can also affect the Z chromosome and potentially also other parts of the genome. Our study provides solid evidence that the repetitive content of the degenerated sex chromosomes is one of the most evolutionary dynamic parts of the genome.

New Secale cereale (rye) DNA derivatives for the detection of rye chromosome segments in wheat

Genome ◽  
1990 ◽  
Vol 33 (5) ◽  
pp. 635-640 ◽  
Author(s):  
C. L. McIntyre ◽  
S. Pereira ◽  
L. B. Moran ◽  
R. Appels
Keyword(s):  
Secale Cereale ◽  
Repetitive Sequence ◽  
Dna Probes ◽  
Entire Length ◽  
Nucleolar Organiser ◽  
Organiser Region ◽  
Nucleolar Organiser Region ◽  
Chromosome Segments

Subcloning of a clone of the 120-bp family of rye, pSc119, has produced two extremely useful probes. pSc119.1 assays rye-specific dispersed repetitive sequence families. It is present on all seven rye chromosomes and hybridizes to the entire length of each chromosome, with the exception of some telomeres and the nucleolar organiser region. pSc119.2, in contrast, hybridizes predominantly to the telomeric regions of rye chromosomes, with some interstitial sites. Unlike pSc119.1, it assays similar repetitive sequence families in both wheat and rye chromosomes.Key words: Secale cereale, rye DNA probes, rye chromosome detection.

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