To determine whether CYFIP1 and NIPA2 were deleted in PWS/AS patients known to have large deletions of chromosome 15q11-q13, we performed FISH experiments on two PWS (PWS-1 and PWS-2) and three AS patients (AS-1, AS-2, & AS-3) using the BAC clones (289D12 and 26F2) where CYFIP1 and NIPA2 were identified (Fig. 4, data from one PWS patient (I, I', J& J') and three AS patients (A to H') are shown). The gene discussed is CYFIP1; the disease is Prader-Willi syndrome.