Abstract: A process for detection of a new polymorphic locus in a DNA sequence is characterized by the following stages. Polynucleotides are prepared by forming an unspecified oligonucleotide including 5 to 10 bases which are repeated 5 to 100 times. A genomic bank is explored by hybridization under low stringency conditions using the prepared polynucleotides which are labelled. The clones that react with the polynucleotides are analyzed by the Southern method. The restriction fragments detected by the polynucleotides are purified and labelled. The genomic DNA of non-consanguineous individuals is analyzed by the Southern method under highly stringent hybridization conditions, with the obtained restriction fragments. The restriction fragments corresponding to new polymorphic loci are selected.