Finding disease genes based on knowledge of their chromosomal location (usually found via linkage analysis in families with the disease) as opposed to knowledge of the function of the gene or protein encoded by the gene.

A process which, through gene mapping techniques, is able to locate a gene responsible for a disease when little or no information is known about the biochemical basis of the disease.

Dr. Francis Collins, director of the National Human Genome Research Institute, defines positional cloning.

Related terms: chromosome, cloning, gene, genetic marker, Human Genome Project.