1. Translation © 2007 Paul Billiet ODWSODWS

2. The tRNA molecule tRNA molecules do the final translating At one end the have a specific amino acid attached by a tRNA activating enzyme These enzymes do the first part of translating At the other end they have an anticodon which is complementary to the mRNA codons © St Edward’s University: Dept Chemistry and Biochemistry © 2007 Paul Billiet ODWSODWS

3. The 3-D structure of a tRNA © ThinkQuest.org

4. The genetic code Made of 64 triplets of bases (codons) © 2007 Paul Billiet ODWSODWS

5. 1 st position 2 nd position 3 rd position ↓ UCAG U PheSerTyrCys U PheSerTyrCys C LeuSerSTOP A LeuSerSTOPTrp G C LeuProHisArg U LeuProHisArg C LeuProGlnArg A LeuProGlnArg G A IleThrAsnSer U IleThrAsnSer C IleThrLysArg A MetThrLysArg G G ValAlaAspGly U ValAlaAspGly C ValAlaGluGly A ValAlaGluGly G AcidicBasicUncharged PolarNon-polar © 2007 Paul Billiet ODWS

6. The degenerate genetic code A few amino acids are coded for by a single codon Most are coded for by more than one codon Some are coded for by up to six codons This is degeneracy in the code © 2007 Paul Billiet ODWSODWS

7. Grammar in the code? Three codons are nonsense codons they represent the end of the information = STOP The codon for methionine found at the beginning of the information to be transcribed it means START The methionine amino acid is usually removed from the finished protein © 2007 Paul Billiet ODWSODWS

8. 1 st positi on ↓ 2 nd position3 rd position ↓ UCAG U PheSerTyrCys U PheSerTyrCys C LeuSerSTOP A LeuSerSTOPTrp G C LeuProHisArg U LeuProHisArg C LeuProGlnArg A LeuProGlnArg G A IleThrAsnSer U IleThrAsnSer C IleThrLysArg A MetThrLysArg G G ValAlaAspGly U ValAlaAspGly C ValAlaGluGly A ValAlaGluGly G © 2007 Paul Billiet ODWSODWS

9. Genetic code: characteristics Only 61 triplets or codons code for amino acids 3 stop codons (aka nonsense codons or terminator codons) UUA UAG UGA © 2007 Paul Billiet ODWSODWS

10. CodonAmino acidCodonAmino acid UUUUUA PhenylalanineLeucine UUCUUG Both pyrimidines Both purines The code is degenerative code Several codons code for the same amino acid The first two letters seem to be the most important the third one tends to be interchangeable © 2007 Paul Billiet ODWSODWS

11. Similar amino acids have similar codons Example Aspartic acid codons GAU and GAC Glutamic acid codons GAA and GAG Both are acidic amino acids © 2007 Paul Billiet ODWSODWS

12. Punctuation? The is no punctuation between each codon The reading frame is set at the beginning of the gene Frame shift mutations can be caused by the ADDITION or DELETION of only one or two bases. Everything downstream is misread © 2007 Paul Billiet ODWSODWS

13. Reading the code The reading of mRNA is always in the same direction 5’ to 3’ (the same way as transcription and replication) The polypeptide chain is constructed from the amino end to the carboxyl end © 2007 Paul Billiet ODWSODWS

14. A universal code The code is used by all organisms So it is very ancient Permits investigations into common ancestry Permits genetically transformed organisms © 2007 Paul Billiet ODWSODWS

15. 20 is the limit Some amino acids are chemically altered AFTER translation. e.g. In collogen proline is converted to hydroxyproline Therefore the total number of amino acids found in proteins is greater than 20 but the total used in translation is only 20 © 2007 Paul Billiet ODWSODWS

16. Translation plan TRANSLATION Polypeptide chain Complete protein Ribosomes Stop codon Start codon © 2007 Paul Billiet ODWSODWS

17. Translation1 AUGGGAUACACUUUUUGA mRNA Ribosome © 2007 Paul Billiet ODWSODWS

18. Translation 2 AUGGGAUACACUUUUUGA met UAC tRNA amino acid anticodon © 2007 Paul Billiet ODWSODWS

19. Translation 3 CCU gly AUGGGAUACACUUUUUGA UAC met © 2007 Paul Billiet ODWSODWS

20. Translation 4 AUGGGAUACACUUUUUGA CCU gly UAC met peptide bond © 2007 Paul Billiet ODWSODWS

21. Translation 5 UAC AUGGGAUACACUUUUUGA CCU glymet AUG tyr © 2007 Paul Billiet ODWSODWS

22. Translation 6 AUGGGAUACACUUUUUGA CCUAUG glymettyr © 2007 Paul Billiet ODWSODWS

23. Translation 7 UGA thr CCU AUGGGAUACACUUUUUGA AUG glymettyr © 2007 Paul Billiet ODWSODWS

24. Translation 8 AAA phe AUGGGAUACACUUUUUGA AUG UGA glymettyr thr polypeptide chain © 2007 Paul Billiet ODWSODWS

25. Translation: the sequence The tRNA molecules with the correct anticodons are lined up with their bases complementary to the mRNA codons Two tRNA molecules at a time can fit on the ribosome A peptide bond forms between their amino acids The first tRNA leaves the ribosome and mRNA move along to accept a new tRNA The process of translation proceeds in the same direction as replication and transcription (5’ to 3’) © 2007 Paul Billiet ODWSODWS