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Genetic mapping in Xenopus
Seifertová, Eva
The diploid amphibian Xenopus tropicalis represents a significant model organism for studies of early development, genes function and evolution. Such techniques as gynogenesis, injection of morpholino antisense oligonucleotide into fertilized eggs or transgenesis were established. In the recent ten years, many efforts have been made to complete the sequence information. X. tropicalis genome has been sequenced but the completion of its assembly only on the basis of sequence data has been impossible. Therefore, our first work was focused on one of approaches for a genome completing- genetic mapping. First of all, the genetic map of Xenopus tropicalis was established pursuant linkage and physical positions of markers. Since the map contained gaps, we developed a new method for genetic mapping based on the next generation sequencing of laser microdissected arm. Using Illumina next generation sequencing of fifteen copies of a short arm of chromosome 7, we obtained new insights into its genome by localizing previously unmapped genes and scaffolds as well as recognizing mislocalized portions of the genome assembly. This was the first time laser microdissection and sequencing of specific chromosomal regions has been used for the purpose of genome mapping. These data were also used in the evolution study of...
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Genetic mapping in Xenopus
Seifertová, Eva ; Krylov, Vladimír (advisor) ; Ráb, Petr (referee) ; Marec, František (referee)
The diploid amphibian Xenopus tropicalis represents a significant model organism for studies of early development, genes function and evolution. Such techniques as gynogenesis, injection of morpholino antisense oligonucleotide into fertilized eggs or transgenesis were established. In the recent ten years, many efforts have been made to complete the sequence information. X. tropicalis genome has been sequenced but the completion of its assembly only on the basis of sequence data has been impossible. Therefore, our first work was focused on one of approaches for a genome completing- genetic mapping. First of all, the genetic map of Xenopus tropicalis was established pursuant linkage and physical positions of markers. Since the map contained gaps, we developed a new method for genetic mapping based on the next generation sequencing of laser microdissected arm. Using Illumina next generation sequencing of fifteen copies of a short arm of chromosome 7, we obtained new insights into its genome by localizing previously unmapped genes and scaffolds as well as recognizing mislocalized portions of the genome assembly. This was the first time laser microdissection and sequencing of specific chromosomal regions has been used for the purpose of genome mapping. These data were also used in the evolution study of...
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Molecular cztogenetic analysis of adaptive radiation in the gecko genus Paroedura (Squamata:Gekkota)
Koubová, Martina ; Kratochvíl, Lukáš (advisor) ; Šťáhlavský, František (referee)
Paroedura genus includes 17 described species endemic to Madagascar and the Comoros Islands, where they went through a significant adaptive radiation. The genus Paroedura is monophyletic and well supported hypothesis on phylogenetic relationships among its species was published. Species vary considerably in body size and morphology and in preferences for habitat, some species live in sympatry. The genus Paroedura belongs to cytogenetically poorly studied family Gekkonidae which exhibits high variability in modes of sex determination and in comparison with basal gecko lineages, also considerable variability in the chromosome number and morphology. Karyotypes of only two species of the genus (P. picta, P. sp.) have been published. The aim of my thesis was to describe karyotypes of both sexes in all available species of the genus using conventional and molecular cytogenetic methods, to perform the phylogenetic analysis of karyotype evolution and chromosomal rearrangements in the genus, to assess the role of these rearrangements in the speciation of the genus and to detect sex chromosomes. I acquired karyotypes of both sexes in nine species representing the most of major phylogenetic lineages of the genus. According to the results, species can be divided into three groups according to diploid...
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Evolution of selected karyotype characters in tetrapulmonate arachnids
Jílková, Klára ; Král, Jiří (advisor) ; Marec, František (referee)
The class Arachnida is not thoroughly explored from the cytogenetic point of view. Previous studies suggest a high diversity of karyotypes and sex determination in arachnids. This study deals with the evolution of sex chomosomes, nucleolar organizer regions (NOR), and telomeric repeats in the tetrapulmonate clade of arachnids, particularly in groups of ancient origin. Sex chromosomes were detected in two orders. Detection of NORs in a large set of species supports the hypothesis that the ancestral karyotype of arachnids contained NOR on one pair of autosomes only. The number of NORs has increased during the evolution of some groups of Pedipalpi. The NORs are located in terminal or subterminal chromosomal regions in most tetrapulmonates. The occurrence of the "insect" telomeric motif was confirmed in majority of tetrapulmonates. Interstitital telomeric repeats were not detected with the exception of one species. Keywords: arachnids, meiosis, sex chromosomes, telomeres, nucleolar organizer, heterochromatin
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Evolution of sex chromosomes and karyotypes in geckos (Squamata: Gekkota)
Koubová, Martina ; Kratochvíl, Lukáš (advisor) ; Choleva, Lukáš (referee)
Gekkota is species-rich and diverse group of squamate reptiles (Reptilia: Squamata) with almost global distribution. There were many hypothesis defined about the phylogeny of this group, traditionally based on morphological data. The essential reversal in phylogenetic relationships occurred with the entry of molecular analysis, whose differ in their conclusions from traditional approach fundamentally, even in positions of mayor lineages. This fact has an essential importance for the karyotype evolution study of this group. The ancestral state is considered as 2n=38 karyotype with all chromosomes acrocentric. In some species is this karyotype kept, in another there is apparent an influence of chromosome changes, mostly Robertsonian fusions and pericentric inversions. Diploid chromosome number is from 16 to 46, but the most common is 2n=38 karyotype of mostly acrocentric chromosomes, gradually decreasing in size. The interesting character of this group is extraordinary variability in sex determining mechanisms. We can find there species with temperature sex determination and also species with genotypic sex determination (both types XX/XY and ZZ/ZW). Sex chromosomes data are documented in only 17 species. Sex chromosomes differ rapidly in their morphology and their homology between sister taxa was not proved...
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Evolution of sex chromosomes and karyotypes in iguanids (Squamata: Iguanidae sensu lato)
Altmanová, Marie ; Kratochvíl, Lukáš (advisor) ; Symonová, Radka (referee)
Iguanids are greatly diversed group of squamate reptiles (Reptilia, Squamata). Although there were many phylogenetical studies made, the relationships among main lineages are still unclear. In cytogenetical point of view is this group relatively conservative. In three species-rich genus only, the diversity of karyotypes is relatively considerable: Anolis, Liolaemus a Sceloporus. Diploid chromosome number varies between 19 and 48. Ancestral karyotype is defined as 2n=36, with 12 macrochromosomes and 24 microchromosomes. Morphologically the macrochromosomes are mostly metacentric, rarely acrocentric or telocentric. In karyotype evolution Robertsonian rearrangements dominate apparently, where number of chromosome arms is preserved. Interspecific variability or variability between populations were observed. Sex seems to be determined by genotype for whole group (GSD). Across the group probably attended conditionally to multiple differentiation of sex chromosomes. In 75 of 219 caryotyped were detected XX/XY type of sex chromosomes or derived multiple sex system X 1X 1X 2X 2/X 1X 2Y. The transition from multiple sex chromosomes back to XX/XY type was observed in one species. Chromosome Y shows morphological variability in size and shape, from microchromosom to huge metacentric macrochromosom. Homology of sex...
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Origin, degeneration and detection of sex chromosomes
Jílková, Klára ; Král, Jiří (advisor) ; Kratochvíl, Lukáš (referee)
Sex chromosomes evolved from a pair of autosomes and they are differentiated as a result of supression of recombination. This process leads to a successive degradation of odd sex chromosome (alosome), which is becoming genetically inert finally or even excluded. Fundamental processes taking part in degeneration of alosome are Muller's ratchet, genetic hitchhiking, background selection, accumulation of transposable elements and constitutive heterochromatin. Indeed, these processes take part in either degeneration of both Y or W chromosomes. Remarkably, these alosomes show different rates of degeneration, most probably due to 1) different structure of male and female gonads as well as 2) different course of gametogenesis in both sexes. Furthermore, rate of alosome degeneration is usually lower in plants because they are haploid during the major part of life cycle. Other mechanisms of sex chromosome evolution involve rearrangements between autosomes and gonosomes, nondisjunctions and fissions of original sex chromosomes, transformation of B chromosomes into sex chromosomes or non-random segregation of autosomes with sex chromosomes. Other phenomenon that appears in sex chromosome evolution is transition between XY/XX and ZW/ZZ systems or transition between chromosomal sex determination and epigamy. Actually,...
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Karyotype analysis of selected representatives of two pedipalpid orders, Amblypygi and Uropygi
Sember, Alexandr ; Král, Jiří (advisor) ; Ráb, Petr (referee)
Karyotype analysis of selected species from arachnid orders Amblypygi and Uropygi Whip spiders (Amblypygi) and whip scorpions (Uropygi) represent relict arachnid orders which has been found already at Upper Carboniferous strata. Although cytogenetic data from amblypygids and uropygids might be important to reconstruct karyotype evolution of arachnids, cytogenetics of these orders is almost unknown. Presented study is aimed in analysis of karyotype and meiosis in 16 species of Amblypygi and 4 species of Uropygi. Both groups are characterized by considerable range of diploid chromosome numbers (2n = 24 - 86 in Amblypygi and 36 - 66 in Uropygi). Analysed species does not exhibit morfologically differentiated sex chromosomes. Differentiation of sex chromosomes on molecular level was revealed in amblypygid Paraphrynus mexicanus by comparative genome hybridization. Obtained data indicate XY/XX sex chromosome system in this species. Comparison of karyotype data indicates reduction of chromosome numbers during evolution of both orders. In Amblypygi, this reduction was accompanied by increase of number of biarmed chromosomes. This trend is not apparent in Uropygi. Karyotypes of most analysed amblypygids and uropygids are also characterized by low amount of heterochromatin. Most studied species exhibit two pairs...
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Určení pohlaví ptáků analýzou DNA
Rádsetoulalová, Iva
In my bachelor thesis -- Determining the sex of birds by DNA analysis, I dealt with covering information about ways of determining sex of birds. I focused on molecular methods, especially sexing birds by analyzing DNA by PCR method, which is based on amplification of CHD1 gen. CHD1 gen is located on both sex chromosomes of almost all bird's species. DNA is getting out of blood samples, feathers or intact membranes. I described avian reproductive system, sex chromosomes, the most common methods of determining sex, PCR method and sex determining genes and genes usable for determining sex of birds.
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Sex chromosomes in the house mouse hybrid zone
DUFKOVÁ, Petra
Understanding the genetic basis of reproductive isolation is the ultimate goal of the study of speciation. Here I present the results of a study of gene flow and its barriers at sex chromosome markers across the central European portion of the hybrid zone between two house mouse subspecies, Mus musculus musculus and M. m. domesticus. We identified strong introgression of Y musculus chromosome into the domesticus area accompanied by a perturbation of the census sex ratio. In addition, we detected stochastic effects that can distort results of hybrid zone studies. Finally, we confirmed a strong effect of sex chromosomes on reproductive isolation and hence their important role in the process of speciation.
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