Fragile X syndrome is a genetic disorder which occurs as a result of a mutation of the "fragile X mental retardation 1" ("FMR1") gene on the X chromosome, most commonly an increase in the number of CGG trinucleotide repeats in the 5' untranslated region of "FMR1". Mutation at that site is found in 1 out of about every 2000 males and 1 out of about every 259 females. Incidence of the disorder itself is about 1 in every 3600 males and 1 in 4000–6000 females. Although this accounts for over 98% of cases, FXS can also occur as a result of point mutations affecting "FMR1".