1. 20 October, 2006 Chapter 15 The Genetic Code

2. Overview The genetic code specifies which codons translate to which amino acids. The genetic code minimizes the effects of mutations. Wobble allows the 5’ base of the anticodon to pair more freely than other bases. There are three stop codons. The code was deciphered using synthetic polynucleotides. tRNA binding to synthetic trinucleotides at the ribosome was also used in deciphering the code. The message is read 5’ to 3’, with nonoverlapping, nondelimited codons in a fixed reading frame. Mutations may be missense, nonsense, or frameshift. The genetic code is nearly universal.

3. Genetic Code

4. The code minimizes the effects of mutations. Mutations in the first base give similar amino acids. Pyr second = hydrophobic, Pur second = polar. (transitions are more copmmon than transversions.) GCn = same, AUn = different (GC is stronger than AU)

5. The code minimizes errors.

6. tRNA

7. Wobble

8. Wobble in the first anticodon position

9. Anticodon Structure

10. Polynucleotide Phosphorylaseand the synthesis of polyA

11. Repeating Sequences

12. Generating Repeating Sequences

13. Deciphering the Code

14. Multiple Frameshifts

15. Second-Site Nonsense Suppression

16. Mitochondrial Genetic Code

18. Title