Linkage AnalysisWe first used the c

Linkage AnalysisWe first used the computer-simulation method of Ott to assess the strength of genetic material for linkage in families M120,HMO10, H12, and H08, with the assumption that a dominant disease with 50% penetrance was present. We then genotyped eight microsatellite markers located in the vicinity of the UBE3A,GABRB3, a5 subunit gene (GABRA5), and g3 subunit gene(GABRG3) cluster on chromosome 15q11.2-12. These markers were selected from the OMIM database and according to the report of Glatt et al.24,25 Two-point linkage analyses were performed with the MLINK and ILINK programs of the LINKAGE software package,version 5.21, under the assumption of autosomal-dominant inheritance with 50% penetrance, with the frequency of the disease allele at 0.001, phenocopy and gene-mutation rates of 1%. The allele frequencies were estimated with the use of the Centre d’Etude du Polymorphisme Humain (CEPH) database.