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Chapter 17

Chapter 17. Transcription and Translation From Gene to Protein. Overview. The “recipe” for a protein is encoded within the DNA One gene, one protein Recipe for one protein is copied into a working version in the form of RNA (Transcription)

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Chapter 17

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  1. Chapter 17 Transcription and Translation From Gene to Protein

  2. Overview • The “recipe” for a protein is encoded within the DNA • One gene, one protein • Recipe for one protein is copied into a working version in the form of RNA (Transcription) • Recipe in RNA is used to make a protein (Translation)

  3. Two Steps Required for Gene Expression • Transcription • Polymerization of RNA molecule from DNA template strand • One gene one transcript • Translation • Production of a protein molecule based on the instructions contained within a mRNA molecule

  4. Transcription • Components • Promotor • TATA box • RNA Polymerase • RNA nucleotides • Termination sequence

  5. Steps in Transcription • Initiation • Elongation • Termination

  6. Transcription Initiation • Transcription factors bind to TATA box • RNA Polymerase joins transcription factors • DNA strands opened • RNA nucleotides aligned

  7. Transcription Elongation • Initiation factors remain at promotor • RNA Polymerase catalyzes building of RNA molecule • 5’-3’ direction of formation of RNA • Continues until termination signal is reached

  8. Transcription Termination • RNA Polymerase reaches the termination signal • Snap back • Rho • Complex destabilization • Release of all components • DNA closes

  9. Movies of Transcription • Transcription

  10. Post Transcriptional ModificationEukaryotes only • 3’ end- poly A tail • 5’ end methylated guanine cap • Exons • Introns • Splicing • Splicosome • Mature mRNA

  11. Post transcriptional Modifications • Splicing

  12. Types of RNA • r RNA - Pol I • m RNA – Pol II • t RNA – Pol III

  13. Translation Manufacture of protein from information in mRNA

  14. Components Involved in Translation • Messenger RNA • Ribosome • A slot • P slot • E slot • Transfer RNA • Amino acids

  15. Terms • Codon • Anticodon • Gene • Chromosome • Genome

  16. Steps found in Translation • Initiation • Elongation • Termination

  17. Initiation of Translation • 5’ end of mRNA • Start codon • AUG • Small sub unit of the ribosome • Initiation tRNA • Methionine • Large sub unit of ribosome • A slot • P slot • E slot

  18. Elongation of Translation • New A.A. bearing tRNA enters the A slot • A.A. transferred from P slot onto AA in A slot • Ribosome slides over one codon • Continues until a stop codon enters the A slot

  19. Termination of Translation • Stop codon enters the A slot • No tRNA H bonds to stop codon • Release factor enters A slot • Peptide chain hydrolysed from the tRNA in the P slot

  20. Movie of Translation • Translation • Musical version

  21. Recap

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