Southern blot hybridization analyses of Ds insertion in the bfl1 mutant and Ds excision in revertants. Genomic DNA (~10 μg) was extracted from putative revertants, digested with HindIII, fractionated on a 0.7% agarose gel, and blotted to a Hybond-N+ membrane. The membrane was hybridised with a gus probe (see Figure 6). PR1 to PR10 are revertants of the original bfl1 mutant and PR2-1 is one of the progenies of PR2. Abbreviations: N, wild-type phenotype; M, mutant phenotype.