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RNA Molecules and RNA Processing

RNA Molecules and RNA Processing. Functions and Modifications of RNA Molecules. transcription. initial transcript RNA. processing. mature RNA. translation. Protein. Information Flow From DNA. replication. DNA. Types of RNA Produced by Transcription. Messenger RNA

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RNA Molecules and RNA Processing

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  1. RNA Molecules and RNA Processing Functions and Modifications of RNA Molecules

  2. transcription initial transcript RNA processing mature RNA translation Protein Information Flow From DNA replication DNA

  3. Types of RNA Produced by Transcription • Messenger RNA Contains the code words for the sequence of amino acids in a specific protein CODON = group of three nucleotidesacting as a code word for an amino acid

  4. Arrangement of Codons on mRNA

  5. anticodon Types of RNA Produced by Transcription • Transfer RNA • “Translates” the message by bringing a specific amino acid into the correct position on the growing protein chain • Has ANTICODON = a group of three nucleotides on a tRNA that recognizes a mRNA codon • Has amino acid attachment site

  6. Types of RNA Produced by Transcription • Ribosomal RNA One of the structural components of the ribosome Ribosome = organelle where protein synthesis occurs Has sites to bind both mRNA and tRNA

  7. Exon 1 intron 1 Exon 2 Exon 3 intron 2 Coding Region Exon 1 Exon 2 Exon 3 Interrupted Genes Eukaryotic Genes have interruptions within regions coding for protein intron = interrupting sequence exon = portion of coding region Processing of the pre-mRNA is required to remove introns and join exons. Translated to Produce Protein

  8. In nucleus Transcription Pre mRNA 5’ 3’ Exon 1 Exon 1 Exon 1 intron 1 intron 1 intron 1 Exon 2 Exon 2 Exon 2 Exon 3 Exon 3 Exon 3 intron 2 intron 2 intron 2 m7G-P-P-P- AAAAAA….. m7G-P-P-P- Protein-coding Region Exon 1 Exon 2 Exon 3 AAAAAA…… m7G-P-P-P- mRNA Processing DNA UTR with consensus sequence Untranslated Region (UTR) Add 5’ cap Cleave at 3’ endAdd 3’ poly-A tail Remove Introns Splice Exons together Stop Codon Start Codon Mature mRNA leaves for cytoplasm

  9. Applying Your Knowledge Which of the following molecules lacks introns? • Pre-mRNA • DNA • Mature messenger RNA • All of these lack introns • None of these lack introns

  10. Intron Removal for Ovalbumin mRNA

  11. Addition of a 5’-Methyl Guanine Cap

  12. Cleavage and Polyadenylation of 3’ end • Pre-mRNA is cleaved 11-30 nucleotides downstream of the AAUAAA consensus sequence. (Rat1 will attach to 5’ end to terminate transcription.) • 50-200 Adenine nucleotides are added enzymatically to the resulting 3’ end.

  13. Identifying Sites for Intron Removal

  14. Steps in Splicing

  15. Alternative Splicing

  16. Multiple 3’ Cleavage Sites

  17. RNA Editing

  18. Applying Your Knowledge A poly-A tail (repeating sequence of adenine nucleotides) is added to _____ of the primary transcript. • The 3’ end • The 5’ end • Either the 3’ end or the 5’ end • Both the 3’ end and the 5’ end • Neither the 3’ end nor the 5’ end

  19. Applying Your Knowledge Which molecule contains the information for assembling the amino acids in the correct order in the protein? • rRNA • tRNA • mRNA • All of these • None of these

  20. tRNA Processing Nucleotide Addition Cleavage Splicing NucleotideModification

  21. rRNA Processing

  22. RNA Interference(RNAi) • Process by which small RNA molecules regulate gene expression • Types of small RNAs • Micro RNAs (miRNAs) • Small Interfering RNAs(siRNAs) • Protein components • Dicer • Protein + RNA = RISC(RNA-Induced Silencing Complex)

  23. Producing Small RNAs

  24. Interfering with RNA Function

  25. Interfering with DNA Function siRNAs • Some siRNAs can inhibit transcription • Protein components • Protein + RNA = RITS(RNA-Induced Transcriptional Silencing) • Methylating Enzyme • Changes the chemical characteristics of DNA or chromatin histone proteins to silence transcription

  26. From different RNA molecules

  27. Gene Silencing by RNA Interference Extra genes for a protein involved in pigment production were introduced into petunia plants. Silencing of both the native and newly-introduced genes led to white flower coloration.

  28. Processes Affected by RNAi • Genomic “Immunity”- protection from viral and transposon genes observed in plants and invertebrates • Regulation of gene expression related to • Development --miRNAs involved in the timing of morphogenesis and maintenance of stem cell populations • Cell fate and proliferation • Cancer • Cell death

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