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- Berkaeva, Maria, et al.
(författare)
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Functional analysis of Drosophila polytene chromosomes decompacted unit: the interband
- 2009
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Ingår i: Chromosome Research. - : Springer Science and Business Media LLC. - 0967-3849 .- 1573-6849. ; 17:6, s. 745-754
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Tidskriftsartikel (refereegranskat)abstract
- Differential compaction of the interphase chromosomes is important for proper functioning of the eukaryotic genome. Such non-uniform compaction is most easily observed in Drosophila salivary gland polytene chromosomes as a reproducible banding pattern. Functional mechanisms underlying the establishment and maintenance of the banding pattern remain unclear but have been hypothesized to involve transcription and chromatin insulators. We tested functional properties of DNA fragments from several transcriptionally inert interband regions that behave as autonomous decompacted units of polytene chromosomes. Our results suggest that, in the absence of transcription, the decondensed state of interband regions does not depend on the presence of insulator elements but instead correlates with the presence of transcriptional enhancers.
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- Blennow, E
(författare)
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Reverse painting highlights the origin of chromosome aberrations
- 2004
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Ingår i: Chromosome research : an international journal on the molecular, supramolecular and evolutionary aspects of chromosome biology. - : Springer Science and Business Media LLC. - 0967-3849. ; 12:1, s. 25-33
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Tidskriftsartikel (refereegranskat)
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- Boman, Jesper, et al.
(författare)
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Meiotic drive against chromosome fusions in butterfly hybrids
- 2024
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Ingår i: Chromosome Research. - : Springer. - 0967-3849 .- 1573-6849. ; 32:2
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Tidskriftsartikel (refereegranskat)abstract
- Species frequently differ in the number and structure of chromosomes they harbor, but individuals that are heterozygous for chromosomal rearrangements may suffer from reduced fitness. Chromosomal rearrangements like fissions and fusions can hence serve as a mechanism for speciation between incipient lineages, but their evolution poses a paradox. How can rearrangements get fixed between populations if heterozygotes have reduced fitness? One solution is that this process predominantly occurs in small and isolated populations, where genetic drift can override natural selection. However, fixation is also more likely if a novel rearrangement is favored by a transmission bias, such as meiotic drive. Here, we investigate chromosomal transmission distortion in hybrids between two wood white (Leptidea sinapis) butterfly populations with extensive karyotype differences. Using data from two different crossing experiments, we uncover that there is a transmission bias favoring the ancestral chromosomal state for derived fusions, a result that shows that chromosome fusions actually can fix in populations despite being counteracted by meiotic drive. This means that meiotic drive not only can promote runaway chromosome number evolution and speciation, but also that it can be a conservative force acting against karyotypic change and the evolution of reproductive isolation. Based on our results, we suggest a mechanistic model for why chromosome fusion mutations may be opposed by meiotic drive and discuss factors contributing to karyotype evolution in Lepidoptera.
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- Borodin, Pavel, et al.
(författare)
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Mendelian nightmares : the germline-restricted chromosome of songbirds
- 2022
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Ingår i: Chromosome Research. - : Springer Nature. - 0967-3849 .- 1573-6849. ; 30:2-3, s. 255-272
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Forskningsöversikt (refereegranskat)abstract
- Germline-restricted chromosomes (GRCs) are accessory chromosomes that occur only in germ cells. They are eliminated from somatic cells through programmed DNA elimination during embryo development. GRCs have been observed in several unrelated animal taxa and show peculiar modes of non-Mendelian inheritance and within-individual elimination. Recent cytogenetic and phylogenomic evidence suggests that a GRC is present across the species-rich songbirds, but absent in non-passerine birds, implying that over half of all 10,500 bird species have extensive germline/soma genome differences. Here, we review recent insights gained from genomic, transcriptomic, and cytogenetic approaches with regard to the genetic content, phylogenetic distribution, and inheritance of the songbird GRC. While many questions remain unsolved in terms of GRC inheritance, elimination, and function, we discuss plausible scenarios and future directions for understanding this widespread form of programmed DNA elimination.
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- Chalopin, Domitille, et al.
(författare)
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Transposable elements and early evolution of sex chromosomes in fish
- 2015
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Ingår i: Chromosome Research. - : Springer Science and Business Media LLC. - 0967-3849 .- 1573-6849. ; 23:3, s. 545-560
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Tidskriftsartikel (refereegranskat)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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