Common Terms for RNA silencing

Over the years, many phenomenon have been observed, but not necessarily understood.  As time has passed and research methods have become more technologically advanced, different phenomenon that were observed and named different things can now be grouped together based off of what is occurring during the phenomenon.  This is exactly what has happened with RNA silencing, therefore, there are many terms that are used to refer to the main process of RNA silencing.  These terms can be considered sub-groups of RNA silencing:

• Cosuppression
• RNA Interference/Post-Transcriptional Gene Silencing
• Quelling

In order to understand the main process of RNA silencing and the specific processes of the sub-groups of RNA silencing, it is important to know different components and features of the processes.  The following is a list of terms that may be futile to your understanding of RNA silencing:

• miRNA (microRNA):  are non coding RNA molecules that are about 22 nucleotides long and are present in both animals and plants. miRNA regulate translation by cleaving off the unwanted portion of the mRNA molecule. This increases the specificity of the polypeptide the miRNA codes for. The presence of hundreds of different miRNA molecules in a single cell makes it clear that majority of protein coding genes are regulated by these molecules.  The following is an illustration of the miRNA process.

• siRNA (small interfering RNA): is a double strand short sequence (twenty or fewer nucleotide bases) of RNA. These molecules bind to a specific portion of mRNA and facilitate the degrading of mRNA. This method is widely used by eukaryotic cells to prevent the production of unwanted polypeptides at a post-transcriptional stage.

• dsRNA (double-stranded RNA): RNA with two complementary strands.  dsRNA makes up the genetic material of many viruses
• ssRNA (single-stranded RNA): The form in which RNA molecules are normally found.
• RISC (RNA-Induced Silencing Complex): A complex made up of a siRNA or miRNA, a dicer, and many proteins.  More detail will be given later on.