<prompt> A 4-year baby is having a large face, large jaw, large ear and macroorchidism isMc Cuneal bright syndromeDowns syndromeCridu chat syndromeFragile X syndrome  <response>: Fragile X syndromeFragile 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 syndromeMental retardation Large testis macroorchidism Large everted earsHyperextensible joint Long face with large mandibleHigh arched palate Mitral valve prolapse 