Mechanistic insight into crossing over during mouse meiosis

SUMMARYCharacteristics of heteroduplex DNA illuminate how strands exchange during homologous recombination, but mismatch correction can obscure them. To investigate recombination mechanisms, meiotic crossover products were analyzed at two hotspots in Msh2–/– mice containing homologous chromosomes derived from inbred strains. Recombination frequencies were unchanged in the mutant, implying that MSH2-dependent recombination suppression does not occur at this level of diversity. However, a substantial fraction of crossover products retained heteroduplex DNA in the absence of MSH2, and some also had multiple switches between parental markers suggestive of MSH2-independent correction. Recombinants appeared to reflect a biased orientation of crossover resolution, possibly stemming from asymmetry at DNA ends established in earlier intermediates. Many crossover products showed no evidence of heteroduplex DNA, suggesting dismantling by D-loop migration. Unlike the complexity of crossovers in yeast, these two modifications of the original double-strand break repair model may be sufficient to explain most meiotic crossing over in mice.

The status of the Hoopoe (Upupa epops) in Hungary: a review

The Hoopoe is a widespread species in Hungary with the strongest populations on the Great plains. The fact that in 2015 it became ‛The Bird of the Year’ in Hungary offers the possibility to summarise the information about the distribution, population size, dispersion, migration as well as the nature conservation status of the Hoopoe population breeding in Hungary. In the period of 1999–2014 the number of breeding pairs and trend of population level was estimated based on the Common Bird Census database. The population size was estimated as 13,500–17,500 pairs with a stable trend (slope=−1.3%, SE=2.5%) over 1999–2014. There is very limited information on migration from bird ringing, only 8 recoveries between 1928–1963 indicate, that the Hungarian population is migrating on a south-southeast direction in autumn, wintering in the eastern parts of the Sahel, possibly in Chad and Sudan and migrates back in spring following a loop migration pattern further to the east. The main conservation issues are agricultural intensification impacting feeding possibilities, lack of nesting cavities and hunting during migration.