RNA interference plays a large role in gene regulation. The process stops the production of faulty or possibly lethal proteins by getting rid of the mRNA molecules which code for these proteins. Basically, RNAi molecules called microRNA (miRNA) and small interfering RNA (siRNA)  attach to “Argonaut” proteins in the cytosol. This miRNA-protein complex travels to the target mRNA molecule and the protein degrades it into its monomer nucleotides. This is possible because the miRNA/siRNA strands are made of complimentary bases to the target mRNA , thus the complex can seek out the target mRNA and attach to it. A more in depth visualisation is available through this link: http://www.nature.com/nrg/multimedia/rnai/animation/index.html
Fig. 1: RNAi process (showing miRNAs) 
Although RNAi occurs naturally, scientists and researchers have taken full advantage of the recent discovery, leading to new technological developments in the biomedical field. SiRNAs are used to treat illnesses and diseases, and also stop the growth and reproduction of some harmful bacteria and viruses. Artificially synthesised siRNA molecules can be injected into a cell. These molecules will then attach to pre-existing argonaut proteins in the cell and carry out the degradation of the target mRNA. This prevents the production of the target proteins and thus will treat the illness caused by the protein, or kill off the bacteria that requires the protein.
Some biomedical firms have taken this RNAi process further by pairing it with recombinant DNA technology. The process is called DNA directed RNAi (ddRNAi) . DdRNAi is a form of gene therapy: DNA (as part of plasmids) that codes for the transcription of siRNA molecules is inserted into the target cell. This DNA then forms part of the cell’s gene and thus siRNAs are continually produced . This will be particularly effective at treating patients with chronic illnesses that continually require the breakdown of a certain protein.
Fig. 2: Recombinant RNAi technology compared to inserting siRNA molecules 
The action of RNAi molecules is one of the leading research subjects in modern biotechnology. Naturally, these molecules help us survive through gene regulation and new technology has helped us to more clearly understand their potential.
 Reece, J. B. et al., 2011. Campbell Biology. 9th (Australian Version) ed. Pearson Australia Group Pty.Ltd
 Nature Reviews 2012. Video Animation: RNA interference. 16/03/12. http://www.nature.com/nrg/multimedia/rnai/animation/index.html
 Carol Potera (GEN) 2012. Firm (Benitec) focuses operations on gene silencing. 20/03/2012. http://www.genengnews.com/gen-articles/firm-focuses-operations-on-gene-silencing/4004/