It is known that Ribonucleic acids or RNAs are nucleic acids constructed from made long nucleotide chains. Micro RNAs which are referred to as miRNA for brevity are single-stranded RNA molecules (Lee et. al. 844). They are about 22 nucleotides long on the average (845). They are encoded by genes which are copied from DNA but are not translated into protein thus making miRNAs non-coding RNAs. miRNAs were discovered back in 1993 by a team of scientists working in the Victor Ambros laboratory (844).
Scientific studies have shown that miRNAs function in gene regulation. Some processes involving miRNAs inhibit protein translation and some facilitate mRNA cleavage (Ruvkun 797). Other studies claim that the miRNA completely blocks protein protein translation machinery without causing mRNA degradation. They may also serve to target methylation of genomic sites that become connected to target mRNAs (798). They function with protein complements that are collectively called miRNP. These behaviors were observed for C. elegans specimens (Lee et. al. 845). Presently, the presence of miRNAs and their function in living bodies have been confirmed in many plants and animals including humans. There are similarly functioning genes that were found in bacteria but they could not be considered as miRNAs because they did not have the same chemical composition (Ruvkun 799).
Lee RC, Feinbaum RL, Ambros V. “The C. elegans heterochronic gene lin-4 encodes small RNAs with antisense complementarity to lin-14.”. Cell 75: 843-854, 1993.
Ruvkun, G. “Molecular biology. Glimpses of a tiny RNA world.”. Science 294 (5543): 797-9, 2001.