It is notable that the occurrence of multiple sex chromosomes differs significantly between major lineages of amniote vertebrates. In this respect, birds are especially conspicuous, as multiple sex chromosomes have not been observed in this lineage so far. On the other hand, in mammals, multiple sex chromosomes have evolved many times independently. We hypothesize that this contrast can be related to the different involvement of sex-specific sex chromosomes in female meiosis subjected to the female meiotic drive under male versus female heterogamety. Essentially, the male-specific Y chromosome is not involved in female meiosis and is therefore sheltered against the effects of the female meiotic drive affecting the X chromosome and autosomes. Conversely, the Z and W sex chromosomes are both present in female meiosis. Nonrandom segregation of these sex chromosomes as a consequence of their rearrangements connected with the emergence of multiple sex chromosomes would result in a biased sex ratio, which should be penalized by selection. Therefore, the emergence of multiple sex chromosomes should be less constrained in the lineages with male rather than female heterogamety. Our broader phylogenetic comparison across amniotes supports this prediction. We suggest that our results are consistent with the widespread occurrence of female meiotic drive in amniotes.
- MeSH
- fylogeneze MeSH
- meióza fyziologie MeSH
- modely genetické MeSH
- plazi genetika MeSH
- pohlavní chromozomy genetika MeSH
- ptáci genetika MeSH
- savci genetika MeSH
- segregace chromozomů fyziologie MeSH
- typy dědičnosti genetika fyziologie MeSH
- zvířata MeSH
- Check Tag
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Klíčová slova
- předsterilizační příprava, kontrola sterilizačního procesu, dokumentace sterilizace, procesové testy sterilizace, chemické testy sterilizace, validace,
- MeSH
- bioindikátory MeSH
- řízení kvality MeSH
- sterilizace * metody normy přístrojové vybavení MeSH
- vojenské lékařství MeSH
- zdravotnická zařízení * normy MeSH
- zdravotnické prostředky MeSH
In contrast to mammals, birds exhibit a slow rate of chromosomal evolution. It is not clear whether high chromosome conservation is an evolutionary novelty of birds or was inherited from an earlier avian ancestor. The evolutionary conservatism of macrochromosomes between birds and turtles supports the latter possibility; however, the rate of chromosomal evolution is largely unknown in other sauropsids. In squamates, we previously reported strong conservatism of the chromosomes syntenic with the avian Z, which could reflect a peculiarity of this part of the genome. The chromosome 1 of iguanians and snakes is largely syntenic with chromosomes 3, 5 and 7 of the avian ancestral karyotype. In this project, we used comparative chromosome painting to determine how widely this synteny is conserved across nine families covering most of the main lineages of Squamata. The results suggest that the association of the avian ancestral chromosomes 3, 5 and 7 can be dated back to at least the early Jurassic and could be an ancestral characteristic for Unidentata (Serpentes, Iguania, Anguimorpha, Laterata and Scinciformata). In Squamata chromosome conservatism therefore also holds for the parts of the genome which are homologous to bird autosomes, and following on from this, a slow rate of chromosomal evolution could be a common characteristic of all sauropsids. The large evolutionary stasis in chromosome organization in birds therefore seems to be inherited from their ancestors, and it is particularly striking in comparison with mammals, probably the only major tetrapod lineage with an increased rate of chromosomal rearrangements as a whole.
- MeSH
- fylogeneze MeSH
- genom MeSH
- hybridizace in situ fluorescenční MeSH
- karyotyp MeSH
- malování chromozomů metody MeSH
- mapování chromozomů MeSH
- metafáze MeSH
- molekulární evoluce MeSH
- plazi genetika MeSH
- ptáci genetika MeSH
- syntenie MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- MeSH
- antibakteriální látky terapeutické užití MeSH
- cholera epidemiologie mortalita terapie MeSH
- dospělí MeSH
- epidemie statistika a číselné údaje MeSH
- hromadné neštěstí ekonomika klasifikace mortalita MeSH
- klinický obraz nemoci MeSH
- lékařské mise ekonomika organizace a řízení MeSH
- lidé MeSH
- tekutinová terapie metody MeSH
- vakcinace metody využití MeSH
- Vibrio cholerae O1 imunologie izolace a purifikace MeSH
- zemětřesení ekonomika klasifikace mortalita MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- mužské pohlaví MeSH
- Publikační typ
- kazuistiky MeSH
- Geografické názvy
- Haiti MeSH
BACKGROUND: The accumulation of repetitive sequences such as microsatellites during the differentiation of sex chromosomes has not been studied in most squamate reptiles (lizards, amphisbaenians and snakes), a group which has a large diversity of sex determining systems. It is known that the Bkm repeats containing tandem arrays of GATA tetranucleotides are highly accumulated on the degenerated W chromosomes in advanced snakes. Similar, potentially homologous, repetitive sequences were found on sex chromosomes in other vertebrates. Using FISH with probes containing all possible mono-, di-, and tri-nucleotide sequences and GATA, we studied the genome distribution of microsatellite repeats on sex chromosomes in two lizard species (the gecko Coleonyx elegans and the lacertid Eremias velox) with independently evolved sex chromosomes. The gecko possesses heteromorphic euchromatic sex chromosomes, while sex chromosomes in the lacertid are homomorphic and the W chromosome is highly heterochromatic. Our aim was to test whether microsatellite distribution on sex chromosomes corresponds to the stage of their heteromorphism or heterochromatinization. Moreover, because the lizards lie phylogenetically between snakes and other vertebrates with the Bkm-related repeats on sex chromosomes, the knowledge of their repetitive sequence is informative for the determination of conserved versus convergently evolved repetitive sequences across vertebrate lineages. RESULTS: Heteromorphic sex chromosomes of C. elegans do not show any sign of microsatellite accumulation. On the other hand, in E. velox, certain microsatellite sequences are extensively accumulated over the whole length or parts of the W chromosome, while others, including GATA, are absent on this heterochromatinized sex chromosome. CONCLUSION: The accumulation of microsatellite repeats corresponds to the stage of heterochromatinization of sex chromosomes rather than to their heteromorphism. The lack of GATA repeats on the sex chromosomes of both lizards suggests that the Bkm-related repeats on sex chromosomes in snakes and other vertebrates evolved convergently. The comparison of microsatellite sequences accumulated on sex chromosomes in E. velox and in other eukaryotic organisms suggests that historical contingency, not characteristics of particular sequences, plays a major role in the determination of which microsatellite sequence is accumulated on the sex chromosomes in a particular lineage.
- MeSH
- genom MeSH
- heterochromatin MeSH
- hybridizace in situ fluorescenční MeSH
- ještěři genetika MeSH
- mikrosatelitní repetice genetika MeSH
- pohlavní chromozomy genetika MeSH
- repetitivní sekvence nukleových kyselin MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The divergence of lineages leading to extant squamate reptiles (lizards, snakes, and amphisbaenians) and birds occurred about 275 million years ago. Birds, unlike squamates, have karyotypes that are typified by the presence of a number of very small chromosomes. Hence, a number of chromosome rearrangements might be expected between bird and squamate genomes. We used chromosome-specific DNA from flow-sorted chicken (Gallus gallus) Z sex chromosomes as a probe in cross-species hybridization to metaphase spreads of 28 species from 17 families representing most main squamate lineages and single species of crocodiles and turtles. In all but one case, the Z chromosome was conserved intact despite very ancient divergence of sauropsid lineages. Furthermore, the probe painted an autosomal region in seven species from our sample with characterized sex chromosomes, and this provides evidence against an ancestral avian-like system of sex determination in Squamata. The avian Z chromosome synteny is, therefore, conserved albeit it is not a sex chromosome in these squamate species.
- MeSH
- fylogeneze MeSH
- genom MeSH
- karyotyp MeSH
- malování chromozomů MeSH
- molekulární evoluce MeSH
- plazi klasifikace genetika MeSH
- pohlavní chromozomy genetika MeSH
- ptáci klasifikace genetika MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- srovnávací studie MeSH
The eyelid geckos (family Eublepharidae) include both species with temperature-dependent sex determination and species where genotypic sex determination (GSD) was suggested based on the observation of equal sex ratios at several incubation temperatures. In this study, we present data on karyotypes and chromosomal characteristics in 12 species (Aeluroscalabotes felinus, Coleonyx brevis, Coleonyx elegans, Coleonyx variegatus, Eublepharis angramainyu, Eublepharis macularius, Goniurosaurus araneus, Goniurosaurus lichtenfelderi, Goniurosaurus luii, Goniurosaurus splendens, Hemitheconyx caudicinctus, and Holodactylus africanus) covering all genera of the family, and search for the presence of heteromorphic sex chromosomes. Phylogenetic mapping of chromosomal changes showed a long evolutionary stasis of karyotypes with all acrocentric chromosomes followed by numerous chromosomal rearrangements in the ancestors of two lineages. We have found heteromorphic sex chromosomes in only one species, which suggests that sex chromosomes in most GSD species of the eyelid geckos are not morphologically differentiated. The sexual difference in karyotype was detected only in C. elegans which has a multiple sex chromosome system (X(1)X(2)Y). The metacentric Y chromosome evolved most likely via centric fusion of two acrocentric chromosomes involving loss of interstitial telomeric sequences. We conclude that the eyelid geckos exhibit diversity in sex determination ranging from the absence of any sexual differences to heteromorphic sex chromosomes, which makes them an interesting system for exploring the evolutionary origin of sexually dimorphic genomes.
- MeSH
- druhová specificita MeSH
- fylogeneze MeSH
- ještěři genetika MeSH
- karyotypizace MeSH
- molekulární evoluce MeSH
- pohlavní chromozomy ultrastruktura MeSH
- pohlavní dimorfismus MeSH
- procesy určující pohlaví MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- MeSH
- dostupnost zdravotnických služeb MeSH
- lékařské mise pracovní síly MeSH
- lidé MeSH
- rozvojové země ekonomika MeSH
- zásobování vodou MeSH
- Check Tag
- lidé MeSH
- Geografické názvy
- Libérie MeSH
- MeSH
- černoši nebo Afroameričané dějiny etnologie psychologie MeSH
- etnicita dějiny etnologie MeSH
- lékařské mise využití MeSH
- lidé MeSH
- občanské nepokoje dějiny etnologie MeSH
- Organizace spojených národů MeSH
- vedení války MeSH
- vojenské lékařství MeSH
- Check Tag
- lidé MeSH
- Geografické názvy
- Česká republika MeSH
- Libérie MeSH
- západní Afrika MeSH
