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101.
Kauppi L Barchi M Baudat F Romanienko PJ Keeney S Jasin M 《Science (New York, N.Y.)》2011,331(6019):916-920
Meiosis requires that each chromosome find its homologous partner and undergo at least one crossover. X-Y chromosome segregation hinges on efficient crossing-over in a very small region of homology, the pseudoautosomal region (PAR). We find that mouse PAR DNA occupies unusually long chromosome axes, potentially as shorter chromatin loops, predicted to promote double-strand break (DSB) formation. Most PARs show delayed appearance of RAD51/DMC1 foci, which mark DSB ends, and all PARs undergo delayed DSB-mediated homologous pairing. Analysis of Spo11β isoform-specific transgenic mice revealed that late RAD51/DMC1 foci in the PAR are genetically distinct from both early PAR foci and global foci and that late PAR foci promote efficient X-Y pairing, recombination, and male fertility. Our findings uncover specific mechanisms that surmount the unique challenges of X-Y recombination. 相似文献
102.
This study was carried out to determine the prevalence of Cryptosporidium species in diarrhoeic lambs and investigate some risk factors in Kars province (Northeastern region of Anatolia) in Turkey.
Four hundred faecal samples were taken from the rectums of clinically diarrhoeic and aged to 1-month-old lambs from 34 sheep
farms in 20 villages in March-April 2007 and examined by using the modified acid-fast staining technique. The prevalence of
Cryptosporidium species was found as 38.8% (155/400). Cryptosporidium oocysts were detected in 90.0% (18/20) of villages and in 76.5% (26/34) of the sheep farms. Infection rates were detected
as: 44.4% (67/151) in 1-week-old lambs, 37.5% (39/104) in 2-week-old lambs, 40.0% (38/95) in 3-week-old lambs, and 22.0% (11/50)
in 4-week-old lambs. Farms classified according to their zoohygienic conditions and fine, average and bad conditioned farms
were contaminated with Cryptosporidium with the percentages of 14.7%, 20.6% and 41.2%, respectively. Clinical cryptosporidiosis was determined in 35.0% of the villages
(7/20) and in 29.4% of the sheep farms (10/34), Cryptosporidium oocysts were found in 81.3% of the lambs (91/112) in these farms. Cryptosporidiosis may be a major epidemiological significance
in lambs in Kars province, and suggests that naturally infected lambs may be reservoirs of Cryptosporidiosis infections for
calves even for humans too. 相似文献