For example, a recent meta-analysis focusing on chromosome-scale recombination landscapes suggested that in plants and animals, recombination rates tend to be higher toward distal parts of chromosomes, and low in chromosome centers ( Haenel et al. hotspots) are mostly species-specific, but some general trends emerge. Nevertheless, when averaged across multiple meioses per individual or in a population, it is clear that COs are not distributed randomly and that some genomic regions act as recombination “jungles” where recombination rates are high, while others act as “deserts” where recombination is low ( Yu et al. It has become clear that recombination rate is not a static “species-specific” or even “individual specific” parameter, since it may vary extensively across the genome, and more generally between populations and sexes, among chromosomes, and even among different meiocytes within an individual (reviewed in Smukowski and Noor 2011 Ritz et al. Therefore, understanding and explaining recombination rates and patterns across the genome remains an important pursuit in biology. Recombination rate measured as a frequency of COs over certain physical distance is a key parameter in evolutionary and population genetic models. From an evolutionary perspective, COs reshuffle genetic variation among parental chromosome copies, creating novel combinations of alleles that contribute to diversity upon which selection can act.
Both the number and placement of COs affect the accuracy of chromosome segregation and may have substantial effects on fertility ( Koehler et al. COs are important in chromosome segregation, forming physical connections between homologs that hold them together into metaphase I, until they segregate toward opposite poles in anaphase I. Crossovers (COs) arise during prophase I of meiosis, the specialized cell division that creates haploid gametes, via orchestrated processes of DNA breakage, chromosome coalignment, pairing, and reciprocal exchange of genetic material between homologous chromosome copies ( Page and Hawley 2003 Gerton and Hawley 2005 Zickler and Kleckner 2015). Homologous recombination in meiosis is a near ubiquitous feature of sexual reproduction in eukaryotes and an important factor in evolution and adaptation. arenosa than in Arabidopsis thaliana.Īrabidopsis arenosa, linkage map, meiotic recombination, crossover, heterochiasmy, outcrossing Introduction We found that averaged genome-wide recombination rate is lower and sex differences subtler in A. We identify several instances of female segregation distortion. We show that the positioning of crossovers along a chromosome correlates with their number, presumably a consequence of crossover interference, and discuss how this effect can cause differences in recombination landscape among sexes or species. We explore how recombination differs at the level of populations, individuals, sexes and genomic regions. We complement the genetic maps with cytological approaches to map and quantify recombination rates, and test the idea that these populations might have distinct patterns of recombination. arenosa individuals from distinct genetic lineages where we have prior knowledge that meiotic genes show evidence of selection. Here, we generate genetic maps for 2 diploid A.
Arabidopsis arenosa is a powerful evolutionary genetic model for studying the molecular basis of adaptation and recombination rate evolution. A good knowledge of recombination landscapes is important for model systems in evolutionary and ecological genetics, since it can improve interpretation of genomic patterns of differentiation and genome evolution, and provides an important starting point for understanding the causes and consequences of recombination rate variation. Despite the functional importance of recombination, recombination landscapes vary widely among and within species, and this can have a strong impact on evolutionary processes. The number and placement of meiotic crossover events during meiosis have important implications for the fidelity of chromosome segregation as well as patterns of inheritance.
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