The invention concerns a method for detecting or locating one or several genes of one or several specific A DNA sequence or one or several molecules reacting with DNA on a B DNA characterised in that it consists in: (a) fixing and combing a certain amount of said B DNA on a combing surface; (b) reacting the product of the B combing with one or several probes, linked with the gene(s) or specific A DNA sequences, or with the molecules capable of reacting with DNA; (c) extracting information corresponding to at least one of the following categories: (1) the position of the probes. (2) the distance between the probes, (3) the size of the probes (the total sum of sizes for quantifying the number of hybridised probes) for determining therefrom the presence, the location and/or the amount of genes or specific A DNA sequences. This method can be used in particular for the diagnosis of genetic diseases.