Genetic variation of wheat landraces in Afghanistan

Dissertação de mestrado em Ensino de Biologia e de Geologia no 3º Ciclo do Ensino Básico e no Ensino Secundário, apresentada ao Departamento de Ciências da Terra e Departamento de Ciências da VidaO presente relatório é referente ao período de Estágio Pedagógico, desenvolvido no âmbito do Mestrado em Ensino de Biologia e de Geologia no 3º Ciclo do Ensino Básico e no Ensino Secundário. O relatório descreve e analisa as atividades organizadas e desenvolvidas durante o estágio realizado na Escola Secundária D. Duarte, durante o ano letivo de 2013/2014. As práticas letivas foram circunscritas ao lecionamento supervisionado dos temas selecionados em Geologia e Biologia do 10º ano. Mais concretamente, os Métodos de estudo para o interior da geosfera e Vulcanologia e o Transporte nas plantas. Neste trabalho participaram alunos de duas turmas tendo sido lecionado o conteúdo de Geologia à turma A e o de Biologia à turma B. As estratégias e os recursos foram avaliados por intermédio de instrumentos de avaliação: diagnóstica (pré-teste e pós-teste, no início e final, respetivamente, de cada um dos períodos de lecionamento); sumativa (questões, específicas dos conteúdos selecionados, e integradas no terceiro e quinto teste sumativo); e questionários. Tanto em Geologia como em Biologia, verificou-se evolução positiva nos resultados do pré para o pós-teste. Relativamente aos testes sumativos, a avaliação foi diferenciada em procedimental e conceptual. Apesar dos resultados positivos a nível conceptual, os alunos revelaram muitas dificuldades a nível procedimental, provavelmente relacionado com o facto de a amostra ter uma média de idades inferior a 15 anos, não tendo sido preparados para o tipo de questões (itens de construção) utilizadas na avaliação procedimental. A análise dos resultados permitiu concluir que as estratégias e recursos tiveram influência na construção dos conhecimentos científicos de Geologia e Biologia. Nos questionários, os alunos também consideraram que as estratégias e recursos contribuíram para as suas aprendizagens. Neste trabalho, identificam-se as limitações das estratégias, dos recursos e dos procedimentos do docente, propondo-se possíveis alternativas e soluções.This report comprises the period of Pedagogical Training, developed within the framework of the Master in Teaching of Biology and Geology in the 3rd Cycle of Basic Education and Secondary Education. The report describes and analyzes the activities organized and carried out during the internship at D. Duarte High School, throughout the academic year of 2013/2014. The practices were confined to the supervised teaching of the selected themes in 10th grade Geology and Biology. Specifically, the Methods of study into the interior of the geosphere and Volcanology and Transport in plants. Students from two classes participated in this work, having been taught the content of Geology in class A and of Biology in class B. Strategies and resources were evaluated by means of assessment tools: diagnostic (pre-test and post-test, respectively in the beginning and end of each of the teaching periods); summative (specific questions of the selected content, and integrated in the third and fifth summative test); and questionnaires. It was ascertain, both in Biology and Geology, a positive development of the results from the pre to the post-test. Regarding summative tests, evaluation was differentiated as procedural and conceptual. Despite the positive results at the conceptual level, students revealed many difficulties in the procedural level, probably related to the fact that the age average of the sample was less than 15 years old and had not been prepared for the type of questions (building items) used in the procedural evaluation. The analysis of the results permitted to conclude that the strategies and resources influenced the construction of scientific knowledge of geology and biology. In the questionnaires, students also felt that the strategies and resources contributed to their learning. In this work are identified the limitations of the strategies, resources and teacher procedures, proposing possible alternatives and solutions

Opacity effects on soft X-ray spectra from highly charged lanthanide ions in laser-produced plasmas

We have observed soft X-ray spectra from highly charged ions of seven different lanthanide elements with atomic numbers ranging from 60 to 70 in laser-produced plasmas (LPPs) using CO2 and Nd:YAG laser systems, the wavelengths of which are 10.6 μm and 1.064 μm, respectively. The spectral feature drastically changes between the two types of LPPs due primarily to the difference in opacity. Narrow band quasicontinuum features arising from n= 4–4 transitions, the centre wavelength of which systematically moves to shorter wavelength as the atomic number (Z) increases, are observed in theCO2LPPs, accompanied by sharp peaks coinciding with the strongest resonance lines of Pd-like ions for lower Z elements. In contrast, the quasicontinuum bands are broader and smoother in the Nd:YAG LPPs, appearing with bands of n= 4–5 transitions on the shorter wavelength side. The results are also discussed based on comparisons with atomic structure calculations for ions with outermost 4d and 4f subshells

Direct and indirect control of the initiation of meiotic recombination by DNA damage checkpoint mechanisms in budding yeast

Meiotic recombination plays an essential role in the proper segregation of chromosomes at meiosis I in many sexually reproducing organisms. Meiotic recombination is initiated by the scheduled formation of genome-wide DNA double-strand breaks (DSBs). The timing of DSB formation is strictly controlled because unscheduled DSB formation is detrimental to genome integrity. Here, we investigated the role of DNA damage checkpoint mechanisms in the control of meiotic DSB formation using budding yeast. By using recombination defective mutants in which meiotic DSBs are not repaired, the effect of DNA damage checkpoint mutations on DSB formation was evaluated. The Tel1 (ATM) pathway mainly responds to unresected DSB ends, thus the sae2 mutant background in which DSB ends remain intact was employed. On the other hand, the Mec1 (ATR) pathway is primarily used when DSB ends are resected, thus the rad51 dmc1 double mutant background was employed in which highly resected DSBs accumulate. In order to separate the effect caused by unscheduled cell cycle progression, which is often associated with DNA damage checkpoint defects, we also employed the ndt80 mutation which permanently arrests the meiotic cell cycle at prophase I. In the absence of Tel1, DSB formation was reduced in larger chromosomes (IV, VII, II and XI) whereas no significant reduction was found in smaller chromosomes (III and VI). On the other hand, the absence of Rad17 (a critical component of the ATR pathway) lead to an increase in DSB formation (chromosomes VII and II were tested). We propose that, within prophase I, the Tel1 pathway facilitates DSB formation, especially in bigger chromosomes, while the Mec1 pathway negatively regulates DSB formation. We also identified prophase I exit, which is under the control of the DNA damage checkpoint machinery, to be a critical event associated with down-regulating meiotic DSB formation

Conformational landscapes of bimesogenic compounds and their implications for the formation of modulated nematic phases

The twist-bend phase (NTB) is most commonly observed in materials with a gross-bent shape: dimers; bent-cores; bent-oligomers. We had suggested previously that the bend-angle of such systems effectively dictates the relative thermal stability of the NTB phase. However, our earlier paper relied on the use of a single energy-minimum conformer and so failed to capture any information about flexibility and conformational distribution. In the present work, we revisit our hypothesis and examine a second set of dimers with varying linking groups and spacer composition. We have improved on our earlier work by studying the conformational landscape of each material, allowing average bend-angles to be determined as well as the conformer distribution. We observe that the stability of the NTB phase exhibits a strong dependence not only on the Boltzmann-weighted average bend-angle (rather than just a static conformer), but also on the distribution of conformers. To a lesser extent, the flexibility of the spacer appears important. Ultimately, this work satisfies both theoretical treatments and our initial experimental study and demonstrates the importance of molecular bend to the NTB phase

Budding yeast ATM/ATR control meiotic double-strand break (DSB) levels by down-regulating Rec114, an essential component of the DSB-machinery

An essential feature of meiosis is Spo11 catalysis of programmed DNA double strand breaks (DSBs). Evidence suggests that the number of DSBs generated per meiosis is genetically determined and that this ability to maintain a pre-determined DSB level, or "DSB homeostasis", might be a property of the meiotic program. Here, we present direct evidence that Rec114, an evolutionarily conserved essential component of the meiotic DSB-machinery, interacts with DSB hotspot DNA, and that Tel1 and Mec1, the budding yeast ATM and ATR, respectively, down-regulate Rec114 upon meiotic DSB formation through phosphorylation. Mimicking constitutive phosphorylation reduces the interaction between Rec114 and DSB hotspot DNA, resulting in a reduction and/or delay in DSB formation. Conversely, a non-phosphorylatable rec114 allele confers a genome-wide increase in both DSB levels and in the interaction between Rec114 and the DSB hotspot DNA. These observations strongly suggest that Tel1 and/or Mec1 phosphorylation of Rec114 following Spo11 catalysis down-regulates DSB formation by limiting the interaction between Rec114 and DSB hotspots. We also present evidence that Ndt80, a meiosis specific transcription factor, contributes to Rec114 degradation, consistent with its requirement for complete cessation of DSB formation. Loss of Rec114 foci from chromatin is associated with homolog synapsis but independent of Ndt80 or Tel1/Mec1 phosphorylation. Taken together, we present evidence for three independent ways of regulating Rec114 activity, which likely contribute to meiotic DSBs-homeostasis in maintaining genetically determined levels of breaks

A High Throughput Genetic Screen Identifies New Early Meiotic Recombination Functions in Arabidopsis thaliana

Meiotic recombination is initiated by the formation of numerous DNA double-strand breaks (DSBs) catalysed by the widely conserved Spo11 protein. In Saccharomyces cerevisiae, Spo11 requires nine other proteins for meiotic DSB formation; however, unlike Spo11, few of these are conserved across kingdoms. In order to investigate this recombination step in higher eukaryotes, we took advantage of a high-throughput meiotic mutant screen carried out in the model plant Arabidopsis thaliana. A collection of 55,000 mutant lines was screened, and spo11-like mutations, characterised by a drastic decrease in chiasma formation at metaphase I associated with an absence of synapsis at prophase, were selected. This screen led to the identification of two populations of mutants classified according to their recombination defects: mutants that repair meiotic DSBs using the sister chromatid such as Atdmc1 or mutants that are unable to make DSBs like Atspo11-1. We found that in Arabidopsis thaliana at least four proteins are necessary for driving meiotic DSB repair via the homologous chromosomes. These include the previously characterised DMC1 and the Hop1-related ASY1 proteins, but also the meiotic specific cyclin SDS as well as the Hop2 Arabidopsis homologue AHP2. Analysing the mutants defective in DSB formation, we identified the previously characterised AtSPO11-1, AtSPO11-2, and AtPRD1 as well as two new genes, AtPRD2 and AtPRD3. Our data thus increase the number of proteins necessary for DSB formation in Arabidopsis thaliana to five. Unlike SPO11 and (to a minor extent) PRD1, these two new proteins are poorly conserved among species, suggesting that the DSB formation mechanism, but not its regulation, is conserved among eukaryotes