Alu elements are non-autonomous retrotransposons present in high number of copies in primate genomes. In the human
genome, these repetitive sequences are interspersed on all chromosomes with more than one million copies. A great variability in Alu density is observed across human genomic regions (1, 2),with a distribution showing two peaks at 0.1 Alu/kb and 1 Alu/kb (3). Thanks to their genome-wide distribution, Alu elements can be used as target loci to perform a PCR-based genome fingerprinting, known as Alu PCR or inter-Alu PCR. The method is characterised by an high information level compared to other DNA fingerprint techniques (4). Alu PCR was originally aimed to isolate human-specific DNA from human–mouse cell hybrids (5), but it has been successively used to detect somatic mutations,
mainly in tumoral samples (6–9), germline genetic variability