Abstract: Many physiological activities take place in the cells of living organisms. These cellular activities are controlled by the genes of the cell. The activities of DNA, RNA and proteins are indispensable for living things. However, the importance of RNA has long been in the shadow of other cellular components, DNA and proteins. Later as the time progress on, this was experimentally demonstrated revealing that during gene expression, DNA is copied in a molecule of messenger RNA (mRNA) that is then translated into proteins molecules. Ribonucleic acid (RNA) is classified in to different categories based on their functions and sizes. Therefore, objectives this review is: to understand the mechanism how RNA interferes, how non-coding RNA regulates gene expression, to understand concept of gene doping and related effects and to understand MicroRNAs and their role for viral diagnosis. The term non-coding RNA (ncRNA) is commonly employed for RNA that does not encode a protein. Cells of living things are self-regulated by the means of interactions between different molecules. RNAs with regulatory function in most cases by base pairing with complementary sequences in other RNAs or DNA, forming RNA: RNA and probably RNA: DNA complexes that are recognized and acted upon by a relatively generic infrastructure (such as RNA-induced silencing complex (RISC) complexes or RNA editing enzymes). On the other hand, RNA interference (RNAi) is a form of Post-Transcriptional Gene Silencing (PTGS) which is regarded as a mechanistic variant of RNAi. MicroRNAs are a group of small, non-coding RNAs which regulate the process of gene expression in a sequence-specific manner. MicroRNAs plays a role in disease diagnosis due to their effort in apoptosis, proliferation of cell, differentiation and development. In generally sense, gene doping is could be defined as “the use of genes, genetic elements and/or cells that have the capacity to enhance athletic performance for non-therapeutic purposes.”