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Once per life cycle, mitotic nuclear divisions are replaced by meiosis I and II - reducing chromosome number from the diploid level to a haploid genome and recombining chromosome arms by crossing-over. In animals, all this happens during formation of eggs and sperm - in yeasts before spore formation. The mechanisms of reciprocal exchange at crossover/chiasma sites are central to mainstream meiosis. To initiate the meiotic exchange of DNA, surgical cuts are made as a form of calculated damage that subsequently is repaired by homologous recombination. These key events are accompanied by ancillary provisions at the level of chromatin organization, sister chromatid cohesion and differential centromere connectivity. Great progress has been made in recent years in our understanding of these mechanisms. Questions still open primarily concern the placement of and mutual coordination between neighboring crossover events. Of overlapping significance, this book features two comprehensive treatises of enzymes involved in meiotic recombination, as well as the historical conceptualization of meiotic phenomena from genetical experiments. More specifically, these mechanisms are addressed in yeasts as unicellular model eukaryotes. Furthermore, evolutionary subjects related to meiosis are treated.
Table des matières
Evolution of Models of Homologous Recombination.- Searching for Homology by Filaments of RecA-Like Proteins.- Biochemistry of Meiotic Recombination: Formation, Processing, and Resolution of Recombination Intermediates.- Meiotic Chromatin: The Substrate for Recombination Initiation.- Meiotic Recombination in Schizosaccharomyces pombe: A Paradigm for Genetic and Molecular Analysis.- Nuclear Movement Enforcing Chromosome Alignment in Fission Yeast-Meiosis Without Homolog Synapsis.- On the Origin of Meiosis in Eukaryotic Evolution: Coevolution of Meiosis and Mitosis from Feeble Beginnings.- The Legacy of the Germ Line - Maintaining Sex and Life in Metazoans: Cognitive Roots of the Concept of Hierarchical Selection.- Lessons to Learn from Ancient Asexuals.
Résumé
Once per life cycle, mitotic nuclear divisions are replaced by meiosis I and II – reducing chromosome number from the diploid level to a haploid genome and recombining chromosome arms by crossing-over. In animals, all this happens during formation of eggs and sperm – in yeasts before spore formation. The mechanisms of reciprocal exchange at crossover/chiasma sites are central to mainstream meiosis. To initiate the meiotic exchange of DNA, surgical cuts are made as a form of calculated damage that subsequently is repaired by homologous recombination. These key events are accompanied by ancillary provisions at the level of chromatin organization, sister chromatid cohesion and differential centromere connectivity. Great progress has been made in recent years in our understanding of these mechanisms. Questions still open primarily concern the placement of and mutual coordination between neighboring crossover events. Of overlapping significance, this book features two comprehensive treatises of enzymes involved in meiotic recombination, as well as the historical conceptualization of meiotic phenomena from genetical experiments. More specifically, these mechanisms are addressed in yeasts as unicellular model eukaryotes. Furthermore, evolutionary subjects related to meiosis are treated.
