Long-range amplification on digested and adaptor-ligated DNA. Genomic DNA is digested with restriction enzymes and the blunt ends of DNA fragments are ligated to an excess of adaptors, made of two complementary oligonucleotides, one long and one short. This technique consists of an amplification between a gene-specific primer and a primer annealing in the adaptor sequence previously ligated to the ends of genomic DNA fragments. The adaptor is designed in such a way that its specific primer cannot anneal on the native adaptor, and the target sequence for the adaptor specific primer (AP1) is therefore only created by elongation from the gene-specific primer. The 3′ extremity of the short oligonucleotide is blocked by an amine group, avoiding its elongation by the DNA polymerase. To increase sensitivity and specificity, a nested amplification is performed using a nested adaptor specific primer (AP2) and a nested gene-specific primer.