<prompt> Which of the following is true about Fragile X syndrome?Triple nucleotide CAG Sequence mutation10 female carriers are mental disabilityAffected males have IQ of 20-40Micro-orchidism in affected males  <response>: Fragile X syndrome Long repeating sequence of three nucleotides. 2nd most common genetic cause of mental retardation after Down syndrome. It is caused by a trinucleotide mutation in the familial mental retardation-1 FMR1 gene CGG Repeat. Affected males are mentally retarded, with an IQ in the range of 20 to 60. Characteristic physical phenotype -Large mandible, large eveed ears, and large testicles macro-orchidism. The most distinctive feature is macro-orchidism in at least 90 of affected post pubeal males. Thiy percent to 50 of carrier females are affected i.e., have intellectual disability. etc. 