2. 1 BIOLOGY PRESENTATIONS FOR A-LEVEL, IN MULTIMEDIA JAMES BOWLES, 2001 BIOLOGY PRESENTATIONS FOR A-LEVEL, IN MULTIMEDIA JAMES BOWLES, 2001 LEFT CLICK OR PRESS SPACE BAR TO ADVANCE, PRESS P BUTTON TO GO BACK, PRESS ESC BUTTON TO END LEFT CLICK OR PRESS SPACE BAR TO ADVANCE, PRESS P BUTTON TO GO BACK, PRESS ESC BUTTON TO END

3. 2 ‘A’ Level Biology Protein Synthesis

4. 3 The Genetic Code The sequence of bases determines the order of amino acids in a protein

5. 4 The code is read in Triplets Triplets of bases This gives 64 combinations of the 4 bases UAAGCGUAUUGGCAUUAAGCGUAUUGGCAUUAAGCGUAUUGGCAUUAAGCGUAUUGGCAU

6. 5 Each triplet is read as a discrete unit The Genetic Code It is a non-overlapping non-overlapping code UAAGCGUAUUGGCAUUAAGCGUAUUGGCAUUAAGCGUAUUGGCAUUAAGCGUAUUGGCAU

7. 6 It is a Degenerate code The Genetic Code GUUGUUGUUGUU GUCGUCGUCGUC GUAGUAGUAGUA GUGGUGGUGGUGValine Most amino acids have more than one triplet coding for them

8. 7 There is also punctuation in the code UAAUAAUAAUAA UAGUAGUAGUAG UGAUGAUGAUGA Stop code

9. 8 The code is universal The Genetic Code Codons code for the same amino acid in all organisms

10. 9 Protein synthesis occurs in three stages: Protein Synthesis 1.Transcription 2.Activation of Amino Acids 3.Translation

11. 10 Part of the DNA molecule unwinds Transcription

12. 11 RNA polymerase attaches at a start codon Transcription

13. 12 RNA polymerase moves along the DNA catalysing the production of mRNA Transcription

14. 13 At the stop codon the RNA polymerase and mRNA detach from the DNA Transcription

15. 14 UACUACUACUAC Activation of Amino Acids Amino Acids combine with tRNA Met

16. 15 UACUACUACUAC Activation of Amino Acids This process utilises specific enzymes and ATP is hydrolysed Met

17. 16 Translation AUGGCGUAUUGGCAUAUGGCGUAUUGGCAUAUGGCGUAUUGGCAUAUGGCGUAUUGGCAUA ribosome attaches to a length of mRNA

18. 17 tRNA with corresponding anticodon fits in the ribosome Translation AUGGCGUAUUGGCAUAUGGCGUAUUGGCAUAUGGCGUAUUGGCAUAUGGCGUAUUGGCAU Met UACUACUACUAC Met UACUACUACUAC Met UACUACUACUAC Met UACUACUACUAC Met UACUACUACUAC

19. 18 A second piece of tRNA fits into the ribosome Translation AUGGCGUAUUGGCAUAUGGCGUAUUGGCAUAUGGCGUAUUGGCAUAUGGCGUAUUGGCAU Met UACUACUACUAC CGCCGCCGCCGC Ala CGCCGCCGCCGC Ala CGCCGCCGCCGC Ala CGCCGCCGCCGC Ala

20. 19 A peptide bond forms between the amino acids Translation AUGGCGUAUUGGCAUAUGGCGUAUUGGCAUAUGGCGUAUUGGCAUAUGGCGUAUUGGCAU Met UACUACUACUAC CGCCGCCGCCGC Ala

21. 20 The ribosome moves along one codon Translation AUGGCGUAUUGGCAUAUGGCGUAUUGGCAUAUGGCGUAUUGGCAUAUGGCGUAUUGGCAU Met UACUACUACUAC CGCCGCCGCCGC Ala CGCCGCCGCCGC

22. 21 The first piece of tRNA is released Translation AUGGCGUAUUGGCAUAUGGCGUAUUGGCAUAUGGCGUAUUGGCAUAUGGCGUAUUGGCAUMet CGCCGCCGCCGC Ala UACUACUACUAC UACUACUACUAC UACUACUACUAC CGCCGCCGCCGC

23. 22 The 1 st amino acid remains in place Translation AUGGCGUAUUGGCAUAUGGCGUAUUGGCAUAUGGCGUAUUGGCAUAUGGCGUAUUGGCAUMet CGCCGCCGCCGC Ala CGCCGCCGCCGC

24. 23 The process is repeated Translation AUGGCGUAUUGGCAUAUGGCGUAUUGGCAUAUGGCGUAUUGGCAUAUGGCGUAUUGGCAUMet CGCCGCCGCCGC Ala AUAAUAAUAAUA Tyr AUAAUAAUAAUA Tyr AUAAUAAUAAUA Tyr AUAAUAAUAAUA Tyr CGCCGCCGCCGC

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