Exon (coding protein) : Sequence of a gene that is represented as m-RNA. Enhancer: Are special cis-acting DNA sequences that increase the rate of initiation of transcription of eukaryotic genes by RNA polymerase II. Leader sequence: Sequence at the 5' end of a mRNA that is not translated into protein. Non-coding RNA (nc RNA): Functional RNA that is not translated into a protein. Non-coding RNAs include tRNA, rRNA, Sno RNA, mi-RNA, si-RNA, pi-RNA and long nc RNA like Xist & HOT AIR.