Large deletion identified in a typical boy with FXS. (A) Representative electrophoresis results for the PCR products of FMR1 for the proband and his normal parents. No products were obtained for the proband, which indicated a large deletion that covered the entire FMR1. P: proband, M: mother, F: father. (B) FISH analysis for leukocytes from the proband using Rp11-161 L9 and Rp11-54I20. As indicated by the white arrows, only the green control signals were observed in the mitoses and nuclei, whereas the targeted orange signal was missing. del(X): X chromosome carrying the deletion.