<P> Approaches to the design of genome - wide RNAi libraries can require more sophistication than the design of a single siRNA for a defined set of experimental conditions . Artificial neural networks are frequently used to design siRNA libraries and to predict their likely efficiency at gene knockdown . Mass genomic screening is widely seen as a promising method for genome annotation and has triggered the development of high - throughput screening methods based on microarrays . However, the utility of these screens and the ability of techniques developed on model organisms to generalize to even closely related species has been questioned, for example from C. elegans to related parasitic nematodes . </P> <P> Functional genomics using RNAi is a particularly attractive technique for genomic mapping and annotation in plants because many plants are polyploid, which presents substantial challenges for more traditional genetic engineering methods . For example, RNAi has been successfully used for functional genomics studies in bread wheat (which is hexaploid) as well as more common plant model systems Arabidopsis and maize . </P> <P> History of RNAi use in medicine </P> <P> The first instance of RNA silencing in animals was documented in 1996, when Guo and Kemphues observed that, by introducing sense and antisense RNA to par - 1 mRNA in Caenorhabditis elegans caused degradation of the par - 1 message . It was thought that this degradation was triggered by single stranded RNA (ssRNA), but two years later, in 1998, Fire and Mello discovered that this ability to silence the par - 1 gene expression was actually triggered by double - stranded RNA (dsRNA). They would eventually share the Nobel Prize in Physiology or Medicine for this discovery . Just after Fire and Mello's ground - breaking discovery, Elbashir et al. discovered, by using synthetically made small interfering RNA (siRNA), it was possible to target the silencing of specific sequences in a gene, rather than silencing the entire gene . Only a year later, McCaffrey and colleagues demonstrated that this sequence specific silencing had therapeutic applications by targeting a sequence from the Hepatitis C virus in transgenic mice . Since then, multiple researchers have been attempting to expand the therapeutic applications of RNAi, specifically looking to target genes that cause various types of cancer . Finally, in 2004, this new gene silencing technology entered a Phase I clinical trial in humans for wet age - related macular degeneration . Six years later the first - in - human Phase I clinical trial was started, using a nanoparticle delivery system to target solid tumors . Although most research is currently looking into the applications of RNAi in cancer treatment, the list of possible applications is extensive . RNAi could potentially be used to treat viruses, bacterial diseases, parasites, maladaptive genetic mutations, control drug consumption, provide pain relief, and even modulate sleep . </P>

How might scientists be able to use srna as therapeutic agents to stop certain diseases