Top: Representative chromatograms of RAI1 sequencing. SMS201 (left) has a deletion of cytosine 1119, just distal to the polyglutamine tract in exon 3 that results in a frameshift leading to misincorporation of 65 amino acids ultimately terminated by a stop codon. Reverse strand sequence is shown, as the forward sequence analysis is obstructed by polymorphic (CAG) repeats. SMS278 (right) carries a deletion of cytosine 4649 in exon 3 that leads to misincorporation of 36 amino acids and a premature stop codon. Sequence for the normal (black) and deleted (red) alleles are shown. (Bottom:) Patients with SMS who have common or unusual 17p11.2 deletions or RAI1 mutations. A–C show individuals with common deletions: (A) SMS111 at 5 y; (B) SMS123 at 3 y. (C) SMS167 at 8.5 y (has a deletion slightly smaller that common deletion, see also Fig. 1.) D–F show individuals with unusual 17p11.2 deletions: (D) SMS143 at 2 y; (E) SMS109 at 8 y; (F) SMS135 at 3 y 8 mon. G–I show individuals with RAI1 mutations: (G) SMS278 at 13 y; (H) SMS153 at 15 years; (I) SMS201 at 6 y.