Picture of Southern blot analysis. EcoRI and EagI double digested DNA samples using radioactive-labelled Stb12.3 probe for Southern blot hybridization. Arrows indicated the 2.8 Kb unmethylated and the 5.2 Kb methylated fragments size. For the case sample we can define the missing 5.2 Kb methylated fragment (circle compassed). POF 283/4, POF 285/4 and POF 287/4 cases indicated those female samples who did not carry FMR1 gene premutation and the background of the POF phenotype should be withstand other genetic deviation. For all these cases we identified two X chromosome normal allels (2,8 kb unmethylated and 5.2 kb methylated).