<prompt> True about Fragile X syndrome is-Triple nucleotide CAG Sequence mutation10 Female carriers mentally retardedMales have IQ 20-40Gain of function mutation  <response>: Solutions: Majority of female carriers of FRAGILE X SYNDROME are mentally normal, 1 in 3 female carriers have some evidence of mental impairment and about 1 in 10 are considered mentally retarded I.e. 10 females are mentally retarded. Mean IQ in males with full mutation 200 repeats is 42 Fragile X syndrome Trinucleotide repeat mutation in familial mental retardation -1 FMR1 gene Second most common genetic cause of mental retardation after Down Syndrome Genetic basis Normal population : 29-55 CGG repeats Carriers: pre-mutatins 55-200 CGG repeats Full mutation Fragile X syndr: 4000 repeats 