cytoplasm ribosomal

In the cytoplasm ribosomal RNA and protein combine to form a nucleoprotein called a ribosome. The ribosome binds mRNA and carries out protein synthesis. Several ribosomes may be attached to a single mRNA at any time.RNA genes sometimes referred to as noncoding RNA or small RNA are genes that encode RNA which is not translated into a protein. The most prominent examples of RNA genes are transfer RNA tRNA and ribosomal RNA rRNA both of which are involved in the process of translation. However since the late s many new RNA genes have been found and thus RNA genes may play a much more significant role than previously thought.In the late s and early there has been persistent evidence of more complex transcription occurring in mammalian cells and possibly others. This could point towards a more widespread use of RNA in biology particularly in gene regulation. A particular class of noncoding RNA micro RNA miRNA has been found in many eukaryotes like rice fruit flies and humans and clearly plays an important role in regulating other genes through a processes called RNA interference RNAi. Although RNA contains only four bases in comparison to the twentyodd amino acids commonly found in proteins certain RNAs are still able to catalyse chemical reactions. These include cutting and ligating other RNA molecules and also the catalysis of peptide bond formation in the ribosome. Doublestranded RNA or dsRNA is RNA with two complementary strands similar to the DNA found in all higher cells. dsRNA forms the genetic material of some viruses. In eukaryotes it acts as a trigger to initiate the process of RNA interference and is present as an intermediate step in the formation of siRNAs small interfering RNAs. siRNAs are often confused with miRNAs siRNAs are doublestranded whereas miRNAs are singlestranded. Although initially single stranded there are regions of intramolecular association causing hairpin structures in premiRNAs immature miRNAs.