Molecular analysis of an unbalanced deletion of the short arm of chromosome 5 that produces no phenotype.

A family has been identified in which an interstitial, apparently unbalanced deletion of the short arm of chromosome 5 could be traced through six individuals in 3 generations. Remarkably, all of the individuals with the deletion are completely asymptomatic and show no physical or mental abnormalities. The deletion was confirmed at the molecular level by identifying DNA probes that mapped within the deleted portion of chromosome 5. Through the use of somatic cell hybrids and quantitative Southern blots, we demonstrated that these individuals do indeed have an unbalanced deletion and are haploid for several million base pairs of DNA in 5p14 without showing any discernable phenotype.