This week in PLoS One, researchers report that missense mutations in FMR1 are not a cause of the Fragile X syndrome phenotype in patients who have normal-length CGG-repeat expansions. To decipher this, the team used an array-based method to sequence FMR1 in 51 individuals exhibiting features of FXS with normal CGG-repeat tracts of the gene. The team suggests that "screening for small deletions of FMR1 may be of clinically utility."