Inverse PCR is a technique to amplify unknown regions flanking the site of transposon insertion using the primers designed from the known sequence from one end of the transposon element. Genomic DNA was digested with a 4-base recognition restriction enzyme, Sau3A1 followed by intramolecular ligation set up at high dilutions. These ligated molecules were then used as templates for the PCR performed with a pair of divergently-oriented primers designed from one end of the transposon named AH1-AH2. The PCR product thus obtained was sequenced with the same set of primers to identify the junction sequence at the site of transposon insertion and hence the identity of the gene disrupted in each case. Typical PCR conditions used were as follows:- Annealing 55°C 2 min Elongation 72°C (1 min/kb of DNA template to be amplified) Denaturation 95°C 2 min After 30 cycles of PCR, the final elongation step was carried out again for 10 min at 72°C