A 4-year baby is having a large face, large jaw, large ear and macroorchidism is –

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. Normally, a codon is triplet (trinucleotide). In these type of disorders, this trinucleotide sequence undergoes amplification and the same sequence is repeated many times in the genome. In most cases, the affected sequences share the nucleotide G and C. Clinical features of fragile - X syndrome Mental retardation                                       Large testis (macroorchidism)                         Large everted ears Hyperextensible joint  Long face with large mandible High arched palate   Mitral valve prolapse