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Journal ArticleDOI

Transposable elements and early evolution of sex chromosomes in fish

TLDR
The role of TEs in the initial steps of differentiation and evolution of sex chromosomes is highlighted, and it is clearly demonstrated that the observed TE-rich sex determination locus originated from a TE-poor genomic region, strengthening the link between TE accumulation and emergence of the sex determination Locus.
Abstract
In many organisms, the sex chromosome pair can be recognized due to heteromorphy; the Y and W chromosomes have often lost many genes due to the absence of recombination during meiosis and are frequently heterochromatic. Repetitive sequences are found at a high proportion on such heterochromatic sex chromosomes and the evolution and emergence of sex chromosomes has been connected to the dynamics of repeats and transposable elements. With an amazing plasticity of sex determination mechanisms and numerous instances of independent emergence of novel sex chromosomes, fish represent an excellent lineage to investigate the early stages of sex chromosome differentiation, where sex chromosomes often are homomorphic and not heterochromatic. We have analyzed the composition, distribution, and relative age of TEs from available sex chromosome sequences of seven teleost fish. We observed recent bursts of TEs and simple repeat accumulations around young sex determination loci. More strikingly, we detected transposable element (TE) amplifications not only on the sex determination regions of the Y and W sex chromosomes, but also on the corresponding regions of the X and Z chromosomes. In one species, we also clearly demonstrated that the observed TE-rich sex determination locus originated from a TE-poor genomic region, strengthening the link between TE accumulation and emergence of the sex determination locus. Altogether, our results highlight the role of TEs in the initial steps of differentiation and evolution of sex chromosomes.

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Journal ArticleDOI

Repetitive DNA in eukaryotic genomes

TL;DR: A range of works involving detailed characterization of the nature of all types of repetitive sequences, in particular their organization, abundance, chromosome localization, variation in sequence within and between chromosomes, and, importantly, the investigation of their transcription or expression activity are overviewed.
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The reversible sex of gonochoristic fish: Insights and consequences

TL;DR: This review discusses sex reversal in gonochoristic fish, with the coexistence of genetic and environmental influences and studies on epigenetics are presented, since it links the environment, gene expression, and sex reversal, notably the association of DNA methylation in sex reversal.
Journal ArticleDOI

Why Do Sex Chromosomes Stop Recombining

TL;DR: Alternative, often neglected, hypotheses for recombination suppression on sex chromosomes, which invoke meiotic drive, heterozygote advantage, and genetic drift, respectively are highlighted.
Journal ArticleDOI

Dynamics of vertebrate sex chromosome evolution: from equal size to giants and dwarfs.

TL;DR: It can be concluded that, due to accumulation of repetitive DNA and transposons, the Y and W chromosomes can increase in size during the initial phase of their differentiation.
References
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Journal ArticleDOI

Basic Local Alignment Search Tool

TL;DR: A new approach to rapid sequence comparison, basic local alignment search tool (BLAST), directly approximates alignments that optimize a measure of local similarity, the maximal segment pair (MSP) score.
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A simple method for estimating evolutionary rates of base substitutions through comparative studies of nucleotide sequences.

TL;DR: Some examples were worked out using reported globin sequences to show that synonymous substitutions occur at much higher rates than amino acid-altering substitutions in evolution.
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Geneious Basic

TL;DR: Geneious Basic has been designed to be an easy-to-use and flexible desktop software application framework for the organization and analysis of biological data, with a focus on molecular sequences and related data types.
Journal ArticleDOI

The zebrafish reference genome sequence and its relationship to the human genome.

Kerstin Howe, +174 more
- 25 Apr 2013 - 
TL;DR: A high-quality sequence assembly of the zebrafish genome is generated, made up of an overlapping set of completely sequenced large-insert clones that were ordered and oriented using a high-resolution high-density meiotic map, providing a clearer understanding of key genomic features such as a unique repeat content, a scarcity of pseudogenes, an enrichment of zebra fish-specific genes on chromosome 4 and chromosomal regions that influence sex determination.
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