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Hoofdstuk 17 2008 deel 1

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Hoofdstuk 17 2008 deel 1

  1. 1. Chapter 17 <ul><li>From gene to protein </li></ul><ul><ul><li>The central dogma: DNA  RNA  protein </li></ul></ul><ul><ul><li>Transcription and translation </li></ul></ul>
  2. 2. Overview <ul><li>Introduction into chapter 17 </li></ul>
  3. 3. Overview <ul><li>Introduction into chapter 17 </li></ul><ul><li>Genes are </li></ul><ul><ul><li>transcribed into (m)RNA </li></ul></ul><ul><ul><ul><li>a transcript may be translated into protein </li></ul></ul></ul>
  4. 4. Overview <ul><li>Introduction into chapter 17 </li></ul><ul><li>Genes are </li></ul><ul><ul><li>transcribed into (m)RNA </li></ul></ul><ul><ul><ul><li>a transcript may be translated into protein </li></ul></ul></ul><ul><li>Genetic code: a triplet encodes an amino acid </li></ul>
  5. 5. Overview <ul><li>Introduction into chapter 17 </li></ul><ul><li>Genes are </li></ul><ul><ul><li>transcribed into (m)RNA </li></ul></ul><ul><ul><ul><li>a transcript may be translated into protein </li></ul></ul></ul><ul><li>Genetic code: a triplet encodes an amino acid </li></ul><ul><li>RNA plays multiple roles during translation </li></ul><ul><ul><li>mRNA </li></ul></ul><ul><ul><li>tRNA </li></ul></ul><ul><ul><li>rRNA </li></ul></ul>
  6. 6. Overview <ul><li>Introduction into chapter 17 </li></ul><ul><li>Genes are </li></ul><ul><ul><li>transcribed into (m)RNA </li></ul></ul><ul><ul><ul><li>a transcript may be translated into protein </li></ul></ul></ul><ul><li>Genetic code: a triplet encodes an amino acid </li></ul><ul><li>RNA plays multiple roles during translation </li></ul><ul><ul><li>mRNA </li></ul></ul><ul><ul><li>tRNA </li></ul></ul><ul><ul><li>rRNA </li></ul></ul><ul><li>Point mutations can effect protein function </li></ul>
  7. 7. From DNA  RNA  protein <ul><li>mRNA is made from 5’  3’ </li></ul><ul><li>Template is read from 3’  5’ </li></ul><ul><li>mRNA is read from 5’  3’ </li></ul><ul><li>Protein is made from N- to C-terminus </li></ul>
  8. 8. Summary, concepts, abbreviations 3’ 5’ 3’ 5’ TATAA ATATT ATG TAC Polymerase <ul><li>ATG has no meaning for RNA polymerase </li></ul>5’ 3’ AUG Ribosome 5’UTR or leader UGA 5’ untranslated region ORF Open reading frame 3’UTR or trailer
  9. 9. Outline chapter 17 <ul><li>From gene to protein </li></ul><ul><li>Transcription </li></ul><ul><ul><li>Initiation </li></ul></ul><ul><ul><li>Elongation </li></ul></ul><ul><ul><li>Termination </li></ul></ul><ul><li>RNA processing </li></ul><ul><li>Protein synthesis </li></ul><ul><ul><li>Initiation </li></ul></ul><ul><ul><li>Elongation </li></ul></ul><ul><ul><li>Termination </li></ul></ul><ul><li>Effect of mutations on proteins </li></ul>
  10. 10. 2 One gene-one enzyme <ul><li>X-ray of bread mold Neurospora crassa </li></ul><ul><li>Look for mutations in survivors in medium, supplemented with </li></ul><ul><ul><li>ornithine </li></ul></ul><ul><ul><li>citrulline </li></ul></ul><ul><ul><li>arginine </li></ul></ul>
  11. 11. 2 One gene-one enzyme <ul><li>X-ray of bread mold Neurospora crassa </li></ul><ul><li>Look for mutations in survivors in medium, supplemented with </li></ul><ul><ul><li>ornithine </li></ul></ul><ul><ul><li>citrulline </li></ul></ul><ul><ul><li>arginine </li></ul></ul>
  12. 12. 2 One gene-one enzyme <ul><li>X-ray of bread mold Neurospora crassa </li></ul><ul><li>Look for mutations in survivors in medium, supplemented with </li></ul><ul><ul><li>ornithine </li></ul></ul><ul><ul><li>citrulline </li></ul></ul><ul><ul><li>arginine </li></ul></ul>
  13. 13. One gene- one enzyme? <ul><li>Not all proteins are enzymes </li></ul><ul><ul><li>Keratin </li></ul></ul>
  14. 14. One gene- one enzyme? <ul><li>Not all proteins are enzymes </li></ul><ul><ul><li>Keratin </li></ul></ul><ul><li>One gene-one protein (True?) </li></ul>
  15. 15. One gene- one enzyme? <ul><li>Not all proteins are enzymes </li></ul><ul><ul><li>Keratin </li></ul></ul><ul><li>One gene-one protein (True?) </li></ul><ul><li>Not all proteins are single chains  </li></ul>
  16. 16. One gene- one enzyme? <ul><li>Not all proteins are enzymes </li></ul><ul><ul><li>Keratin </li></ul></ul><ul><li>One gene-one protein (True?) </li></ul><ul><li>Not all proteins are single chains  </li></ul><ul><li>One gene-one polypeptide? </li></ul>
  17. 17. One gene- one enzyme? <ul><li>Not all proteins are enzymes </li></ul><ul><ul><li>Keratin </li></ul></ul><ul><li>One gene-one protein (True?) </li></ul><ul><li>Not all proteins are single chains  </li></ul><ul><li>One gene-one polypeptide? </li></ul><ul><li>Is tRNA or rRNA encoded by a gene? </li></ul>
  18. 18. 3 Transcription-translation <ul><li>DNA  RNA  protein </li></ul><ul><li>In eukaryotes </li></ul><ul><ul><li>Initial RNA= premRNA or primary transcript </li></ul></ul><ul><ul><li>NOT mRNA </li></ul></ul><ul><li>Ribosome is protein-synthesis factory </li></ul>
  19. 19. 3 Transcription-translation <ul><li>DNA  RNA  protein </li></ul><ul><li>In eukaryotes </li></ul><ul><ul><li>Initial RNA= premRNA or primary transcript </li></ul></ul><ul><ul><li>NOT mRNA </li></ul></ul><ul><li>Ribosome is protein-synthesis factory </li></ul>
  20. 20. 3 Transcription-translation <ul><li>DNA  RNA  protein </li></ul><ul><li>In eukaryotes </li></ul><ul><ul><li>Initial RNA= premRNA or primary transcript </li></ul></ul><ul><ul><li>NOT mRNA </li></ul></ul><ul><li>Ribosome is protein-synthesis factory </li></ul><ul><li>Eukaryote: transcription </li></ul><ul><li>and translation separated </li></ul><ul><li>by the nuclear membrane </li></ul>
  21. 21. Translating nucleotides into amino acids <ul><li>How can 4 nucleotides encode 20 different amino acids? </li></ul><ul><li>A doublet of nt’s? </li></ul><ul><ul><li>4 2  16 aa </li></ul></ul><ul><ul><li>4 3  64 aa, sufficient and OK </li></ul></ul><ul><li>Triplet code </li></ul>
  22. 22. 4 Triplet code <ul><li>Polarity!! </li></ul><ul><li>Two strands of DNA </li></ul><ul><ul><li>Sense and </li></ul></ul><ul><ul><li>Template </li></ul></ul><ul><li>mRNA is complement of template, not a copy </li></ul><ul><li>Triplets in mRNA code for aminoacids: </li></ul>codons
  23. 23. Complementarity ! <ul><ul><li>WE ALWAYS GO FROM 5’  3’ </li></ul></ul><ul><ul><li>DNA is made from 5’  3’ </li></ul></ul><ul><ul><li>mRNA is made from 5’  3’ </li></ul></ul><ul><ul><li>We read from 5’  3’ </li></ul></ul><ul><ul><li>So: the codon for Phenylalanine (Phe, F) is UUC, in the template GAA </li></ul></ul>DNA: 5’ TTC 3’ 3’ AAG 5’ RNA: 5’ UUC 3’ protein: NH2- Phe- COOH
  24. 24. Translation <ul><li>Codons in mRNA are translated (by the ribosome) one by one, three nucleotides at the time into amino acids. </li></ul><ul><li> a 42,000 Da or 450 aa protein is encoded by at least 1350 nucleotides in mRNA or 1350 basepairs in DNA </li></ul>
  25. 25. 5 The genetic code <ul><li>Nearly universal </li></ul><ul><li>Special is AUG </li></ul><ul><li>Degeneration (’ontaard’) or redundancy, ‘wobble’ </li></ul><ul><ul><li>6 codons for </li></ul></ul><ul><ul><ul><li>Leu L (click) </li></ul></ul></ul><ul><ul><ul><li>Ser S (click) </li></ul></ul></ul><ul><ul><ul><li>Arg R (click) </li></ul></ul></ul><ul><ul><li>4 codons for </li></ul></ul><ul><ul><ul><li>Val V (click) </li></ul></ul></ul><ul><ul><ul><li>Ala A (click) </li></ul></ul></ul><ul><ul><ul><li>Pro P (click) </li></ul></ul></ul><ul><ul><ul><li>Gly G (click) </li></ul></ul></ul><ul><ul><ul><li>Thr T (click) </li></ul></ul></ul><ul><li>Play with this code! </li></ul><ul><li>How to start translation? </li></ul><ul><ul><li>Reading frame </li></ul></ul>
  26. 26. 5 The genetic code <ul><li>Nearly universal </li></ul><ul><li>Special is AUG </li></ul><ul><li>Degeneration (’ontaard’) or redundancy, ‘wobble’ </li></ul><ul><ul><li>6 codons for </li></ul></ul><ul><ul><ul><li>Leu L (click) </li></ul></ul></ul><ul><ul><ul><li>Ser S (click) </li></ul></ul></ul><ul><ul><ul><li>Arg R (click) </li></ul></ul></ul><ul><ul><li>4 codons for </li></ul></ul><ul><ul><ul><li>Val V (click) </li></ul></ul></ul><ul><ul><ul><li>Ala A (click) </li></ul></ul></ul><ul><ul><ul><li>Pro P (click) </li></ul></ul></ul><ul><ul><ul><li>Gly G (click) </li></ul></ul></ul><ul><ul><ul><li>Thr T (click) </li></ul></ul></ul><ul><li>Play with this code! </li></ul><ul><li>How to start translation? </li></ul><ul><ul><li>Reading frame </li></ul></ul>
  27. 27. How did they find out the codon code? <ul><li>Add poly(U) to E. coli translation extract </li></ul><ul><ul><li>poly-phenylalanine was made </li></ul></ul>
  28. 28. How did they find out the codon code? <ul><li>Add poly(U) to E. coli translation extract </li></ul><ul><ul><li>poly-phenylalanine was made </li></ul></ul><ul><li>Add poly(AU) to extract </li></ul><ul><ul><li>peptide made of isoleucine (AUA) and tyrosine (UAU) </li></ul></ul><ul><ul><li>61 triplets or codons encode amino acids </li></ul></ul><ul><ul><li>3 triplets encode termination or stop-signals </li></ul></ul>
  29. 29. Reading frame <ul><li>AGA GAA GCU GAU AUU CAG GGA </li></ul><ul><li>R E A D I N G </li></ul>
  30. 30. Reading frame <ul><li>AGA GAA GCU GAU AUU CAG GGA </li></ul><ul><li>R E A D I N G </li></ul><ul><li>x GAG AAG CUG AUA UUC AGG GA.. </li></ul><ul><li>E K L I F R - </li></ul>
  31. 31. Reading frame <ul><li>AGA GAA GCU GAU AUU CAG GGA </li></ul><ul><li>R E A D I N G </li></ul><ul><li>x GAG AAG CUG AUA UUC AGG GA.. </li></ul><ul><li>E K L I F R - </li></ul><ul><li>The red dog ate the cat </li></ul><ul><li>T her edd oga tet hec at  </li></ul><ul><li>How doe sar ibo som ekn owt hes tar t? </li></ul>

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