Hybridization-based mapping of Neurospora crassa linkage groups II and V

As part of the German Neurospora crassa genome project, physical clone maps of linkage groups II and V of N. crassa were generated by hybridization-based mapping. To this end, two different types of clone library were used: (1) a bacterial artificial clone library of 15-fold genome coverage and an average insert size of 69 kb, and (2) three cosmid libraries--each cloned in a different vector--with 17-fold coverage and 34 kb average insert size. For analysis, the libraries were arrayed on filters. At the first stage, chromosome-specific sublibraries were selected by hybridization of the respective chromosomal DNA fragments isolated from pulsed-field electrophoresis gels. Subsequently, the sublibraries were exhaustively ordered by single clone hybridizations. Eventually, the global libraries were used again for gap filling. By this means, physical maps were generated that consist of 13 and 21 contigs, respectively, and form the basis of the current sequencing effort on the two chromosomes.