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Glossary of Terms

antisense A piece of DNA that produces a mirror image (or antisense) mRNA that is opposite in sequence to the one that directs protein synthesis. The RNA will bind tightly to its mirror image, thus preventing the production of the particular protein.

C. elegans (Caenorhabditis elegans) A nematode worm that is relatively as primitive an organism as exists but shares many of the essential biological characteristics that comprise predominant concerns of human biology, making it an ideal laboratory research subject. It was used as the basis of study for the pioneering RNAi work of the Guo, S./Kemphues, K.J. and the Fire et al research teams.

Dicer An enzyme in the RNase III family of dsRNA-specific ribonucleases that processes dsRNAs into siRNAs.

ddRNAi (DNA-directed RNA interference) A method for gene silencing in which a DNA segment is introduced into cells, triggering the production of dsRNA. The dsRNA is cleaved into siRNA, which destroys the target mRNA. Patented by Benitec Ltd. In March 1998.

dsRNA (double-stranded RNA) RNA with two complementary strands; similar to DNA found in more complex cells. dsRNA has the ability to directly suppress and silence target genes, in that the process is founded on the basis that cells destroy RNA when it is double-stranded.

eiRNA (expressed interfering RNA) RNA used in an environment in which plasmid DNA coding for relevant dsRNA is inserted into targeted cells, allowing them to generate and convey specific dsRNA sequences that cleave into targeted gene silencing siRNAs.

gene A unit of hereditary material that forms a discrete component of the chromosome of most organisms encoding data in the form of a DNA sequence

gene silencing The suppression or interruption of the expression of a gene at a transcriptional or translational level.

IP (intellectual property) Intangible property that is the result of creativity, such as patents, trademarks and copyrights, and is allowed exclusive rights by intellectual property law over these intangibles on the equivalence of property rights, whether for a specified or indefinite period of time.

mRNA (messenger RNA) RNA that carries instructions from DNA to ribosomes for the synthesis of a protein.

NCBI RefSeq database (The National Center for Biotechnology Information Reference Sequence database) A repository, under the aegis of the National Institutes of Health, of comprehensive, integrated, non-redundant sets of predicted and annotated sequences, including genomic DNA, transcript (RNA), and protein products for major research organisms. The database serves as the standard for the basis for medical, functional, and diversity studies, and provides a reliable reference for gene identification and characterization, mutation analysis, expression studies, polymorphism discovery, and comparative analyses, and is used as a reagent for the functional annotation of genome sequencing projects, including those of human and mouse.

patent pool (as defined and referenced by the USPTO) An agreement between two or more patent owners to license one or more of their patents to one another or third parties. Alternatively, a patent pool may also be defined as "the aggregation of intellectual property rights that are the subject of cross-licensing, whether they are transferred directly by patentee to licensee or through some medium, such as a joint venture, set up specifically to administer the patent pool."

protein The chemical building block from which cells, organs, and tissues are constructed. Proteins also serve as hormones, enzymes and antibodies, and are made of long chains of even smaller building blocks called amino acids, which determine the size, shape, and length of protein molecules

reagent Any substance used in a chemical reaction, particularly as an element that is added to bring about the chemical change.

ribozyme (RNA enzyme) An RNA molecule that can initiate the catalysis of a chemical reaction.

RISC (RNA-induced silencing complex) A nuclease complex, composed of proteins and siRNA, which targets and destroys endogenous mRNAs complementary to the siRNA within the complex.

RNA (ribonucleic acid) A nucleic acid comprised of a string of covalently bonded (formed by shared non-ionic electrons) nucleotides, and differentiated from DNA by the presence of an auxiliary hydroxyl group that is appended to each pentose ring, as well as by the use of uracil rather than thymine. RNA transcriptionally conveys the genetic information from DNA into proteins.

RNAi (RNA interference) A mechanism in which the presence of small fragments of dsRNA, with a sequence matching a given gene, interferes with the expression of that gene but does not appear to interact with the DNA; post-transcriptional gene silencing (PTGS) caused by the introduction of double-stranded RNA (dsRNA). The process occurs when long dsRNAs are cleaved by the enzyme Dicer in siRNAs, which are then recruited to an RNA-induced silencing complex which mediates the cleavage of the target mRNA. Andrew Fire and Craig Mello coined the name in 1998, when injecting dsRNA into C. elegans.

shRNA (short hairpin RNA) A short sequence of RNA that makes a tight hairpin turn and can be in sequence-specific gene silencing in mammalian cells.

siRNA (small interfering RNA) Also called "guide RNAs," these 20-25 nucleotide-long dsRNAs can induce post-transcriptional gene silencing when introduced in cells.

USPTO (United States Patent and Trademark Office) An agency of the United States Department of Commerce which promotes the progress of science and the useful arts by giving inventors the exclusive right to their respective discoveries for limited periods of time. Its primary services are processing patent and trademark applications and disseminating patent and trademark information. www.uspto.gov.