Abstract: The invention relates to fields of use of unlabelled polynucleotide probes able to form hairpins, the biochips comprising such probes and methods allowing use thereof. The present invention also concerns methods for designing such probes and biochips. More particularly, the invention concerns the use of such unlabelled probes and biochips for manipulating and analysing polynucleotide sequences and optionally molecules which are associated therewith. This invention further concerns methods for preparing and use such probes and biochips for analysing mutations, sequencing, detection of alternative splicing variants, gene expression analysis, analysis of allelic imbalances and loss of heterozygosity and the detection of any nucleic acid present in organisms or residues from said organisms.