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Evolution of sex-determining mechanisms and genomes in squamate reptiles (Reptilia: Squamata)
Pokorná, Martina ; Kratochvíl, Lukáš (advisor) ; Marec, František (referee) ; Vyskot, Boris (referee)
Evolution of sex determining mechanisms in squamate reptiles (Reptilia: Squamata) Martina Pokorná Ph.D. thesis Abstract This Ph.D. thesis is focused on the evolution of sex determining mechanisms and genomes in squamate reptiles. It is based on three published articles and two manuscripts. The evolution of sex determining mechanisms, sex chromosomes and genomes, and their organisation, was studied on a wide phylogenetic scale of the whole group of squamate reptiles and some lineages of other Sauropsids, as well as on the small phylogenetic range as a detailed comparative study inside individual lineages of squamates. This thesis is based upon the use of classical cytogenetic methods, methods of molecular cytogenetic (especially fluorescent in situ hybridisation) and the results were analysed using phylogenetic approaches. The results and outputs of this study represent an important contribution to the general knowledge of the principals of sex determination and the evolution of these phenomena not only in squamate reptiles but also in the whole group of amniotes. Using the results obtained during the work on this thesis we can conclude that sex chromosomes evolved in particular lineages of amniotes independently. This origin was in some cases followed by accumulation of microsatellite sequences on sex...
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Physical mapping of genome regions without linkage map using BAC clones in Xenopus tropicalis
Špirhanzlová, Petra ; Krylov, Vladimír (advisor) ; Marec, František (referee)
Xenopus leavis was a favorite model organism during the 20th. century, but nowadays it has been replaced by diploid Xenopus tropicalis, which has not only shorter generation time, but also smaller genom. One of the disadvantages of Xenopus tropicalis is the lack of full physical and linkage map. According to JGI genome database (assembly 4.1) there are unmapped regions on short arm of the chromosome 2 and 7 . Several BAC clones ( with a single or dual-end sequence) has been found to be located within this region, according to a recent assembly 7.1. However , it isn't clear whether 100bp length of BAC ends is enough to place entire BAC clone into the genom of Xenopus tropicalis. In order to prove correct inclusion of these BAC clones into JGI database, several BAC clones, which are supposed to be located on short arm of chromosome 2, were picked. Using fluorescence in situ hybridisation, the signal of these BAC clones was localised on the short arm of chromosome 1 instead of chromosome 2 and in most cases they had opposite orientation. It means that the 100bp lenght of BAC ends propably isn't sufficient to place entire BAC clone on chromosome. New working protocol of BAC DNA isolation and labeling was established.
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Cytogenetics and biology of selected representatives of the family Sphaeriidae
Kořínková, Tereza ; Juřičková, Lucie (advisor) ; Reise, Heike (referee) ; Marec, František (referee)
"Cytogenetics and biology of selected representatives of the family Sphaeriidae" Mgr. ing. Tereza Kořínková Abstract of a PhD. thesis The thesis has a form of four separate articles, the full texts of which are included. Two of them were published, one was accepted and one was under revision before submission of the PhD thesis. The articles deal with cytogenetics, breeding and nutrition of selected representatives of the hermaphroditic, viviparous, primarily freshwater bivalves of the family Sphaeriidae (Mollusca: Bivalvia: Veneroida). Although various aspects of the biology of Sphaeriidae have been intensely studied for more than 100 years, many questions still remained unresolved. This thesis brings data on chromosome numbers of 11 species(10 of which have not been studied cytogenetically before) and information on the course of meiosis in two of these species (Chapter 1). Although the chromosome numbers are high (from ca. 140 to more than 240), the behaviour of chromosomes at meiosis rather corresponds to that of diploid organisms. Also the DNA contents in five selected species with high chromosome numbers (as measured by flow- cytometry) do not differ significantly from those in sphaeriids with a diploid chromosome number of 30. Such results contradict an origin of the high chromosome numbers by a...
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Molecular cytogenetics of selected actinopterygian fishes: insight from repetitive sequences to whole genome analyses
Majtánová, Zuzana ; Symonová, Radka (advisor) ; Marec, František (referee) ; Šťáhlavský, František (referee)
Actinopterygian fishes exhibit the greatest taxonomical diversity of all vertebrates, making this group attractive to address numerous evolutionary questions. The role of molecular cytogenetics and cytogenomics further increase because recent advances in these fields provide more comprehensive view of fish genome organization and evolutionary dynamics, responsible for this amazing diversity. My Thesis investigates the genome organization of selected fish lineages, namely basal lineages of Actinopterygians (Lepisosteidae and Amiidae) and Teleosts (Pantodontidae), together with "modern" fishes Cobitidae and Coregonidae. I have integrated conventional and molecular cytogenetic techniques together with phylogenetic and statistical approaches. Publications included into the Thesis describe e.g. the cytogenetic variability and dynamics in closely related fish species of the genus Coregonus and the impact of repetitive sequences on the ecological speciation. In contrast to the recent cytotaxonomical diversity of Coregonids, we have detected a karyotype stability associated with asexual reproduction in spined loaches of the genus Cobitis. In the subsequent publication, we describe a surprising AT/GC genome organization in gars (Atractosteus and Lepisosteus) and summarize the knowledge of genome...
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