7q11.23 deletions in Williams syndrome arise as a consequence of unequal meiotic crossover.

Williams syndrome (WS) is a multisystem disorder characterized by mental retardation, a specific neurobehavioral profile, characteristic facies, infantile hypercalcemia, cardiovascular abnormalities, progressive joint limitation, hermas, and soft skin. Recent studies have shown that hemizygosity at the elastin (ELN) gene locus on chromosome 7q is associated with WS. Furthermore, two FISH studies using cosmid recombinants containing the 5{prime} or the 3{prime} end of the ELN gene revealed deletion of the entire ELN gene in 90%-96% of classical WS cases. However, the size of the 7q11.23 deletions and the mechanism by which these deletions arise are not known. 15 refs., 2 figs., 1 tab.