1. Chapter 8: Bacterial Genetics

2. Genetic changes in bacteria occur via: -mutations -gene transfer

3. What are mutations? Change in the base sequence of the DNA Do they always change the genetic code?

4. Causes of mutations in bacteria Most are spontaneous Errors made by DNA Polymerase UV light exposure

5. Types of Mutations Base-pair mutation –Missense mutation –Nonsense mutation –Silent mutation

6. Base-pair mutation: missense

7. Results of base-pair mutations

8. Types of Mutations Frameshift –Changes the reading frame

9. What can cause mutations? Chemicals (nitrous acid) Physical mutagens (uv light) Biological mutagens (transposons)

10. Barbara McClintock: “jumping genes” biological mutagen

11. Nitrous acid as a chemical mutagen

12. Nitrosoguanidine alters guanine bases

13. Nucleoside analogs are mutagens

14. Intercalating agents

15. UV light as a mutagen

16. Repair mechanisms Wrong nucleotide inserted –Proofreading –Mismatch repair

17. Repair: Mismatch

18. Repair of UV damage Two repair mechanisms –Light repair –Dark repair

19. Why use bacteria to study mutations? Only have one chromosome…one copy of each gene Easy to grow

20. Direct selection Testing for traits that are easily identified –Colony color –Motility –Resistance to antibiotics

21. Indirect selection A way to look at traits that are not easily identified, at changes in metabolic pathways Replica plating –A way to identify AUXOTROPHS from PROTOTROPHS

22. Replica Plating: indirect selection

23. Penicillin enrichment of mutants

24. Testing chemicals for mutagenicity…Ames test