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Basics of RNA structure RNA functions Storage/transfer of genetic information • Genomes • many viruses have RNA genomes single-stranded (ssRNA) e.g., retroviruses (HIV) double-stranded (dsRNA) • Transfer of genetic information • mRNA = "coding RNA" - encodes proteins RNA functions Structural • e.g., rRNA, which is a major structural component of ribosomes BUT - its role is not just structural, also: Catalytic RNA in the ribosome has peptidyltransferase activity • Enzymatic activity responsible for peptide bond formation between amino acids in growing peptide chain • Also, many small RNAs are enzymes "ribozymes" RNA functions Regulatory Recently discovered important new roles for RNAs In normal cells: • in "defense" - esp. in plants • in normal development e.g., siRNAs, miRNA As tools: • for gene therapy or to modify gene expression • RNAi • RNA aptamers Aptamers : are oligonucleic acid that bind to a specific target molecule. RNA types & functions Types of RNAs Primary Function(s) mRNA - messenger translation (protein synthesis) regulatory rRNA - ribosomal translation (protein synthesis) t-RNA - transfer translation (protein synthesis) hnRNA - heterogeneous nuclear precursors & intermediates of mature mRNAs & other RNAs scRNA - small cytoplasmic signal recognition particle (SRP) tRNA processing <catalytic> snRNA - small nuclear snoRNA - small nucleolar mRNA processing, poly A addition <catalytic> rRNA processing/maturation/methylation <catalytic> regulatory RNAs (siRNA, miRNA, regulation of transcription and translation, etc.) other?? Types of RNA Genetic information copied from DNA is transferred to 3 types of RNA: __________ RNA: mRNA Copy of information in DNA that is brought to the ribosome and translated into PROTEIN by tRNA & rRNA. ( 2%) , 100,000 KINDS. __________ RNA: rRNA Most of the RNA in cells is associated with structures known as ribosomes, the protein factories of the cells.(80%), FEW KINDS It is the site of translation where genetic information brought by mRNA is translated into actual proteins. ___________ RNA: tRNA Brings the amino acid to the ribosome that mRNA coded for. (15%), 100 KINDS.