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Fig. 17-17

Initiating translation. Large ribosomal subunit. 3 . U. 5 . C. A. P site. Fig. 17-17. Met. Met. 5 . 3 . A. G. U. Initiator tRNA. GDP. GTP. E. A. mRNA. 5 . 5 . 3 . 3 . Start codon. Small ribosomal subunit. Translation initiation complex. mRNA binding site.

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Fig. 17-17

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  1. Initiating translation Large ribosomal subunit 3 U 5 C A P site Fig. 17-17 Met Met 5 3 A G U Initiator tRNA GDP GTP E A mRNA 5 5 3 3 Start codon Small ribosomal subunit Translation initiation complex mRNA binding site

  2. Amino end of polypeptide E 3 mRNA P site A site Ribosome ready for next aminoacyl tRNA 5 GTP Fig. 17-18-4 GDP E E P A A P GDP GTP E P A

  3. Terminating translation Fig. 17-19-3 Release factor Free polypeptide 5 3 3 3 2 GTP 5 5 Stop codon (UAG, UAA, or UGA) 2 GDP

  4. Translation animation How is this model different than what is in your textbook? How are aminoacyl-tRNAs brought to the ribosome? How are hydrogen bonds represented? How is the expenditure of energy (GTP) represented? What is “peptidylsynthetase”?

  5. Fig. 17-3a-2 DNA TRANSCRIPTION mRNA Ribosome TRANSLATION Polypeptide (a) Bacterial cell

  6. Promoter Transcription unit 5 3 3 5 DNA Start point RNA polymerase Initiation 1 5 3 Fig. 17-7a-4 3 5 Template strand of DNA RNA transcript Unwound DNA Elongation 2 Rewound DNA 5 3 3 3 5 5 RNA transcript Termination 3 5 3 3 5 3 5 Completed RNA transcript

  7. RNA polymerase DNA mRNA In bacteria: Translation can happen while transcription is still ocurring Polyribosome Fig. 17-24 0.25 µm Direction of transcription RNA polymerase DNA Polyribosome Polypeptide (amino end) Ribosome mRNA (5 end)

  8. Fig. 18-3a In bacteria: Many genes are organized in operons Operon = group of genes sharing one promoter, expressed as 1 mRNAs containing multiple ORFs trp operon Promoter Genes of operon trpD trpE trpC trpB trpA Stop codon Start codon mRNA 5 B A D C E Polypeptide subunits that make up enzymes for tryptophan synthesis

  9. Nuclear envelope DNA TRANSCRIPTION Fig. 17-3b-3 Pre-mRNA RNA PROCESSING mRNA TRANSLATION Ribosome Polypeptide (b) Eukaryotic cell

  10. A eukaryotic promoter includes a TATA box 1 Promoter Template 5 3 3 5 TATA box Template DNA strand Start point Several transcription factors must bind to the DNA before RNA polymerase II can do so. 2 Fig. 17-8 Transcription factors 5 3 3 5 Additional transcription factors bind to the DNA along with RNA polymerase II, forming the transcription initiation complex. 3 RNA polymerase II Transcription factors 3 5 5 5 3 RNA transcript Transcription initiation complex

  11. A eukaryotic mRNA Fig. 17-9 Polyadenylation signal Protein-coding segment 5 3 … G AAA AAA P P P AAUAAA 5 Cap Poly-A tail Start codon 5 UTR 3 UTR Stop codon

  12. Many eukaryotic mRNAs are spliced Exon Exon Intron 5 Exon Intron 3 Fig. 17-10 Pre-mRNA Poly-A tail 5 Cap 146 31 104 1 105 30 Introns cut out and exons spliced together Coding segment mRNA 5 Cap Poly-A tail 1 146 5 UTR 3 UTR

  13. RNA transcript (pre-mRNA) 5 Exon 1 Intron Exon 2 Protein Other proteins snRNA snRNPs Fig. 17-11-1

  14. RNA transcript (pre-mRNA) 5 Exon 1 Intron Exon 2 Protein Other proteins snRNA snRNPs Fig. 17-11-2 Spliceosome 5

  15. RNA transcript (pre-mRNA) 5 Exon 1 Intron Exon 2 Protein Other proteins snRNA snRNPs Fig. 17-11-3 Spliceosome 5 Spliceosome components Cut-out intron mRNA 5 Exon 2 Exon 1

  16. Gene DNA Exon 1 Intron Exon 2 Intron Exon 3 Transcription Fig. 17-12 RNA processing Translation Domain 3 Domain 2 Domain 1 Polypeptide

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