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RNA 3 major classes: mRNA 2-5% tRNA 10-15% rRNA 80-85%

RNA 3 major classes: mRNA 2-5% tRNA 10-15% rRNA 80-85% mRNA - number of different mRNAs in a cell can range from 100s to 1000s & sizes can differ from 100s to 1000s nucleotides In bacteria, mRNA synthesized, utilized and degraded continually so constant turnover, t1/2 of mRNA ~2 min

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RNA 3 major classes: mRNA 2-5% tRNA 10-15% rRNA 80-85%

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  1. RNA 3 major classes: mRNA 2-5% tRNA 10-15% rRNA 80-85% mRNA - number of different mRNAs in a cell can range from 100s to 1000s & sizes can differ from 100s to 1000s nucleotides In bacteria, mRNA synthesized, utilized and degraded continually so constant turnover, t1/2 of mRNA ~2 min tRNA - most cells have 60-70 different tRNAs (74-95 nts) rRNA - E.Coli ribosomes have: 5S (120 nt), 16S (1542 nt), 23S (2904 nt) Eukaryotic ribosomes have: 5S (145 nt), 18S (1869 nt), 28S (5025 nt), 5.8S (157 nt) In eukaryotes, mitochondria & chloroplasts contain DNA and ribosomes, so euks can have > 1 different sets of mRNAs, tRNAs and rRNAs Other (non-coding) ncRNAs: snRNA (small nuclear) - involved in mRNA synthesis, removal of intervening seq and polyadenylation snoRNA (small nucleolar) - process rRNA precursors in euk nuclei 7S RNA - in cytoplasmic RNP, involved in transport of proteins through membrane siRNA (small interfering) - 20-25 nt double-stranded RNA molecules that play a variety of roles in biology, most notably in RNA interference (RNAi) piRNA (piwi interacting) - 29-30 nt RNA molecules expressed in mammalian testes; forms RNA-protein complexes with Piwi proteins; complex linked to transcriptional gene silencing of retrotransposons and other genetic elements in germ line cells gRNA (guide) - RNA that guides the insertion of uridines into mRNAs in trypanosomes in a process known as RNA editing Riboswitches - RNA elements found in non-coding regions of mRNA molecules, gene expression is modulated when metabolite binds directly to the RNA. Many riboswitches, once liganded, repress expression of nearby genes involved in the synthesis of the metabolite, providing an efficient feedback mechanism of genetic control Also other catalytic RNA molecules - RNA molecules capable of self-splicing and self-cleavage

  2. Nucleotides & Nucleic Acids Hydrolysis of RNA

  3. Nucleotides & Nucleic Acids RNA structure Single-stranded (ss) RNAs

  4. Nucleotides & Nucleic Acids RNA structure - M1 RNA from RNase P

  5. Nucleotides & Nucleic Acids RNA structure - rRNA

  6. Nucleotides & Nucleic Acids RNA structure - tRNA

  7. Nucleotides & Nucleic Acids RNA structure - tRNA  = pseudouridine I = inosine T = ribothymine D = 5,6-dihydrouridine m1I = 1-methylinosine m1G = 1-methylguanosine m2G = 2-methylguanosine Pu = purine Py = pyrimidine G* = 2’-O-methylguanylate

  8. +7 Bulge loop Interior loop Bulge loop Interior loop

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