Which is not true about Fragile X syndrome ?

Ans. is 'b' i.e., Pigmented nevi Fragile - X syndrome Fragile - X syndrome is the prototype of diseases in which the mutation is characterized by a long repeating sequence of three nucleotides. o In fragile X syndrome,trinucleotide repeat mutation involve CGG on non coding region. o Clinical features of fragile - X syndrome Mental retardation Long face with large mandible Hyperexntesible joint Mitral valve prolapse Large eveed ears Large testis (macro-orchidism) High arched palate o Fragile X syndrome is the second most common cause of mental retardation, after Downs syndrome.