Which of the following is true about Fragile X syndrome?
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.)
Triple nucleotide CAG Sequence mutation
10% female carriers are mental disability
Affected males have IQ of 20-40
Micro-orchidism in affected males
NEET 2019