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RNA

Definition

Ribonucleic acid; a polynucleotide formed by the polymerization of the ribonucleotides adenosine triphosphate, guanosine triphosphate, cytosine triphosphate and uracyl triphosphate. RNA usually occurs as single-stranded molecules, although extensive intramolecular base pairing causes it to assume complex secondary structures. It serves as genome in certain viruses but in other cells it accomplishes a number of vital roles in the passage of information from DNA (qv) to proteins. DNA-based genetic information is transferred to RNA by the process of transcription in which messenger RNA molecules (mRNA) are neosynthesized using the DNA as a template. This information is then used to order amino acid incorporation in protein synthesis by the process of translation. In this process individual amino acids are positioned in the protein chain by transfer RNA molecules (tRNA) as the mRNA passes through subcellular particles known as ribosomes, The ribosomes themselves consist of protein and ribosomal RNA (rRNA).

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