Mapping translocation breakpoints by orthogonal field agarose-gel electrophoresis

Orthogonal field agarose-gel electrophoresis (OFAGE) of chromosomes from translocation-bearing and normal Neurospora crassa strains was utilized, first, to recover cosmids from a translocated region, and second, to map translocation breakpoints. Surprisingly, the right breakpoints in two independently derived, interstitial translocations, T(II-->III) AR18 and T(II-->VI)P2869, are within about 5.6 kbp of each other suggesting that this region of linkage group (LG) II may be fragile or otherwise subject to chromosome breakage. Mapping translocation breakpoints through OFAGE, or other similar methods, should allow for DNA sequencing across breakpoints that are not associated with mutant phenotypes or that are not within walking distance of cloned markers.