image: This shows a direct image of DNA fibers from soybean chromosome, revealing that soybean variety "Fayette" is resistant to soybean cyst nematodes due to the presence of ten direct-repeat copies of a four-gene block carrying genes that confer SCN resistance. Susceptible soybean varieties carry only one copy of these four genes. Composite image shows diagram of the repeat (top) and four extended DNA fibers detected using fiber-FISH method (fluorescence in-situ hybridization). White scale bar (lower right) corresponds to 10 µm (ten micrometers), which corresponds to approximately 32,000 DNA base-pairs. This image relates to a paper that appeared in the Oct. 11, 2012, issue of Science Express, published by AAAS. The paper, by David Cook at University of Wisconsin, Madison in Madison, Wis., and colleagues was titled, “Copy Number Variation of Multiple Genes at Rhg1 Mediates Nematode Resistance in Soybean.” view more
Credit: [Image courtesy of Kai Wang and Jiming Jiang]