[Highly-effective subtractive hybridization of cDNA]

A scheme for subtractive hybridization is described allowing for a 500-1000 fold enrichment of low abundant cDNA. The scheme is based on the previously described principle of normalization of an initial mixture of differently represented cDNAs in the single-stranded portion of a tracer after the first round of subtraction and the principle of a trapper excluding the fraction of the double-stranded cDNAs formed during the first round from the subsequent PCR-amplification. The technique is simple and makes unnecessary the separation of the tracer, driver and hybrids formed after the subtraction.