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Sperm morphology and motility in estrildid finches of the genus Lonchura
Šárová, Markéta ; Reifová, Radka (advisor) ; Frolíková, Michaela (referee)
Sexual selection plays an important role in the evolution of animals. Today we already know that it takes place not only before copulation (precopulatory sexual selection), but also after copulation. This type of sexual selection is called postcopulatory sexual selection, and occurs mainly in promiscuous species, where females mate with multiple males. In this case, sperm competition occurs in the female reproductive tract. To increase the likelihood of their reproductive success, males began to develop surprisingly diverse sperm adaptations at the morphological, physiological, or behavioural levels. These adaptations often affect sperm velocity (motility), which is a key factor for successful egg fertilization. However, the result of reproductive success can also be influenced by females, who may prefer sperm with a certain phenotype in the process of cryptic female choice, and thus, for example, obtain better genes for offspring. In some species, females even can have the ability to sort and store sperm in specialized organs in which the sperms are nourished for some time, and then used to fertilize the egg. Even in this case, the storage of sperm is often affected by sperm morphology. Due to these mechanisms of postcopulatory sexual selection, sperm are under strong selection pressure, which can...
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Inferring the demographic history of populations from genomic data
Simandlová, Sára ; Reifová, Radka (advisor) ; Černá Bolfíková, Barbora (referee)
Currently, it is not difficult to obtain genomic data even from non-model organisms. These data can give us information about the demographic history of populations. Many statistical inference methods have been developed to infer the demographic history of populations from genomic data, which I describe in this bachelor thesis. At first, I introduce the reader to important concepts in analyzing the demographic history of populations. I then describe the different types of genomic data that can be used to infer the demographic history of populations. Next, I discuss statistical methods, which include methods based on site frequency spectrum data, methods using approximate Bayesian computation, methods for determining identity, and sequential Markov coalescent methods. I provide a basic overview of the theory and logic of each approach. I then present procedures for selecting inference methods. Keywords: population genetics, demographic inference, statistical inference, whole genome data
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Meiotic effect of MutS homolog 6 (Msh6) mutation in two mouse subspecies
Fusek, Karel ; Forejt, Jiří (advisor) ; Reifová, Radka (referee)
To study hybrid sterility our laboratory uses mouse strains PWD/Ph (PWD), derived from Mus musculus musculus wild mice and the common laboratory strain C57BL/6J (B6) mostly of Mus musculus domesticus origin as a model. Crossing between PWD female and B6 male results in sterile male progeny. F1 hybrid males carry defects in the repair mechanisms of asymmetric double-strand DNA breaks (DSBs). Functional interplay of SPO11 and PRDM9 proteins in the meiotic prophase I is necessary for repairs. Its defect leads to incorrect synapse formation between homologous chromosomes, leading to halt in spermatogenesis and thus male sterility. The formation of DSBs and their subsequent repair is essential for first meiotic division. The working hypothesis stems from the findings in yeast model, where supposed antirecombinatorial mechanism of mismatch repair genes Msh6 and Msh2 prevents DSBs repairs during meiosis. Despite the functional mechanism of these two genes is not explicitly known, existence of similar repair system in mice is presumed. Variety of methods was implemented in this thesis. The effects of Msh6 deletion on meiotic prophase I and sperm maturation were performed by designing guide RNAs for CRISPR/Cas9 for creation of three knock-outs in B6 mice. The PCR was used to amplify regions adjacent to the...
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Detection of positive selection on the molecular level
Cakl, Lukáš ; Reifová, Radka (advisor) ; Munclinger, Pavel (referee)
The rise in computational power and available genomic data has made it possible to examine the traces of selection on nucleic acid sequences. To gain the most relevant results, we need to know how are said traces created, what are their properties, how to detect them and which methods to use in a given set of circumstances. This bachelor thesis is dedicated not only to the methods we use to detect positive selection and their underlying principles, but also to the theoretical models, which allowed their conception, neutral theories, against which we test our traces and the traces themselves. Due to the dynamic nature of the genome, alongside the data we have available, the properties of the selection traces are the most important factor for picking one of the methods we have available. Especially since, speaking in the terms of an evolutionary scale, certain traces are created swiftly and disappear soon afterwards, while the formation of others requires large periods of time. Keywords: darwinian selection, positive selection, statistical methods, selection detection, dna, molecular data
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Postcopulatory sexual selection
Kivader, Tomáš ; Reifová, Radka (advisor) ; Tomášek, Oldřich (referee)
Sexual selection is a key evolutionary process which affects transfer of gene's alleles to future generations. We distinguish precopulatory and postcopulatory sexual selection. Postcopulatory sexual selection is a type of sexual selection which takes place after copulation, more specifically after insemination. During precopulatory sexual selection same-sex individuals compete over the opportunity to reproduce. Simultaneously, males and females have different priorities. Males prefer quantity while females quality of offspring. So they compete in creating new strategies for increasing their own fitness. Consequently, sexual selection often leads to coevolution between males and females of the same species. Finally, this affects the segregation of individual populations and speciation. For establishing postcopulatory sexual selection it is important that multiple males are mating with the same female within the scope of one population. This is ensured by promiscuity or extra-pair copulations in various mating systems. There are two basic processes by which postcopulatory sexual selection is realized. Those are sperm competition and cryptic female choice. These mechanisms have not been explored in detail yet. Firstly, because monitoring postcopulatory processes in vivo is problematic, and secondly,...
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Programmed DNA elimination in animals
Janáková, Šárka ; Reifová, Radka (advisor) ; Choleva, Lukáš (referee)
Programmed DNA elimination (PDE) is a process in which a part of genetic information is eliminated from the organisms genome. It can be found be found in both plants and animals. There is a difference in the genetic inormation eliminated depending on the species. There are some organisms that eliminate only parts of their chromosomes, others that eliminate whole chromosomes and in hybrid organisms one whole parental genome is eliminated. In somatic cells PDE usually takes place during early embryogenesis. If the genome being eliminated comes from the germline cells, PDE takes place during gametogenesis. The function and mechanisms of PDE differs inbetween the species. It is most often connected with soma and germ cell differentiation, sex determination in animals and haploid gamete production in hybrid species. Mechanisms frequently include epigenetic modifications of DNA destined for elimination or production of micronuclei (MN) with the eliminated DNA inside. This work summarizes these functions and mechanisms and provides examples. Key words: programmed DNA elimination, chromatin diminution, chromosomal elimination, hybridogenesis, micronuclei, epigenetic modifications, Germ1, GRC
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The role of interspecific competition in ecological differentiation and speciation in two passerine species, Luscinia megarhynchos and Luscinia luscinia
Sottas, Camille Pauline ; Reifová, Radka (advisor) ; Krist, Miloš (referee) ; Sedláček, Ondřej (referee)
(in English) Interspecific competition is assumed to play an important role in the morphological and ecological differentiation of co-occurring species and could contribute to their speciation. However, empirical studies showing a direct association between competition, ecological niche divergence and specific morphological adaptations are scarce. This thesis focuses on the role of interspecific competition in the differentiation and the evolution of reproductive isolation between two closely related passerine species: the common nightingale (Luscinia megarhynchos) and the thrush nightingale (Luscinia luscinia). Both species are insectivorous and have similar ecological niches. They have diverged 1.8 Mya and their areas currently overlap in a secondary contact zone, where both species still occasionally hybridize. Previous studies have reported an accentuate bill size divergence in sympatric populations compared to allopatric populations, suggesting that interspecific competition might have resulted in feeding niche divergence between the two species in sympatry. Within this PhD thesis, I have studied potential associations between bill morphology divergence, diet composition, habitat use and gut microbiota composition. We found that the two nightingale species have diverged in feeding niche in...
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Sperm motility and postmating prezygotic isolation in two nightingale species
Baránková, Lucie ; Reifová, Radka (advisor) ; Frolíková, Michaela (referee)
The motility of male gametes (sperm) is one of the important factors influencing the reproductive success of males. Because sperms are often subjected to strong postmating sexual selection and even closely related species often differ in sperm morphology, sperm motility could also differ between species, which may contribute to reproductive isolation between species. As part of my diploma thesis, I studied sperm motility in two closely related species of songbirds, the common nightingale (Luscinia megarhynchos) and the thrush nightingale (Luscinia luscinia). These two species of nightingales are an ideal model system because the areas of these two species overlap in the secondary contact zone across Central and Eastern Europe, where they occasionally hybridize and thus allow the study of speciation mechanisms in the natural environment. Both species also differ greatly in total sperm length. As part of my diploma thesis, I studied the possible influence of different sperm morphology on their motility. I further tested whether the motility of nightingale sperm differs in the fluid from the cloaca of a female of the same species and a different species, which would demonstrate the presence of postmating prezygotic reproductive isolation between species. The results of my work showed that despite the...
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Speciation genomics in nightingales
Mořkovský, Libor ; Reifová, Radka (advisor) ; Macholán, Miloš (referee) ; Piálek, Lubomír (referee)
Speciationisusuallyaslowprocessoccurringoverthousandstomillionsofyears.Thismakes speciation research difficult because no direct observation or manipulation is possible. At best, we can gain some insight by inferring the population history and structure in very fine detail by investigating genetic markers in multiple individuals of the nascent species. Today, speciationresearchisinanunprecedentedpositionthankstotheadventofhigh-throughput sequencingmethods,whichmakeiteasier and cheaper than ever before to evaluate multiple markers in many individuals. Speciation is not a straightforward process that happens in the same way every time, but rather a phenomenon occurring when genetic and ecological circumstancesactinginsymphonyultimatelyleadtoreproductiveisolationoftwosubpopula- tions. This is why it is important to study multiple model systems to understand the general principles behind speciation. We worked with two species of nightingales (Luscinia luscinia andL.megarhynchos)thatdivergedapproximately1.8Mya,likelyduetoglacialfluctuations in Europe. Our main goal was to use these new high-throughput sequencing methods to (1) detect interspecific hybrids between the species, (2) estimate levels of interspecific gene flow,(3)findareasofthenightingalegenomethatunderliereproductiveisolationand,finally, (4)...
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Meiosis and fertility of juvenile mouse males
Valtrová, Pavlína ; Trachtulec, Zdeněk (advisor) ; Reifová, Radka (referee)
This work is a summary of literature on pecularities of spermatogenesis in juvenile mouse males (Mus musculus) and their utilization. Spermatogenesis is a process that leads through meiosis to sperm production. The cell undergoes in waves the following cell types: spermatogonia, spermatocytes, spermatids, and spermatozoa. Juvenile mice (whose testes size and sperm count have not reached their maximum) are often used to study individual cell types. The transition between cell types takes shorter time in juveniles. Spermatozoa from the 1st wave of spermatogenesis (WS) are derived from prenatal gonocytes, allowing earlier sperm production. They have a lower frequency of crossing over (CO rate) due to a different processing of CO intermediates; the consequence can be aneuploidy (one chromosome less/more). Spermatozoa from the 2nd WS still display lower CO rate. In 3rd WS testes descend and their temperature decreases to 33řC; CO rate is more like in adults. In 4th WS is typical testicular supportive cells mature and CO rate is similar to adult levels. Juvenile males also suffer from more frequent and severe sperm malformations. Low CO rate should not have an impact on fertility; errors are eliminated during meiotic checkpoints. However, the children of young fathers have a higher risk of aneuploidy,...
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