1. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings M I C R O B I O L O G Y a n i n t r o d u c t i o n ninth edition TORTORA  FUNKE  CASE Part B 8 Microbial Genetics

2. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Translation  mRNA is translated in codons (three nucleotides)  Translation of mRNA begins at the start codon: AUG  Translation ends at a stop codon: UAA, UAG, UGA PLAY Animation: Translation Figure 8.2

3. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Translation Figure 8.8

4. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Translation Figure 8.10

5. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Regulation of Bacterial Gene Expression  Constitutive enzymes are expressed at a fixed rate.  Other enzymes are expressed only as needed.  Repressible enzymes  Inducible enzymes

6. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Operon PLAY Animation: Operons Figure 8.12, step 1

7. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Regulation of Gene Expression Figure 8.13

8. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Mutation  A change in the genetic material  Mutations may be neutral, beneficial, or harmful.  Mutagen: Agent that causes mutations  Spontaneous mutations: Occur in the absence of a mutagen

9. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings  Base substitution (point mutation)  Missense mutation Mutation  Change in one base  Result in change in amino acid Figure 8.16a–b

10. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings  Nonsense mutation Mutation  Results in a nonsense codon Figure 8.16a, c

11. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Mutation  Frameshift mutation  Insertion or deletion of one or more nucleotide pairs Figure 8.16a, d

12. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Mutation  Ionizing radiation (X rays and gamma rays) causes the formation of ions that can react with nucleotides and the deoxyribose-phosphate backbone.  Nucleotide excision repairs mutations.

13. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Mutation  UV radiation causes thymine dimers.  Light-repair separates thymine dimers. Figure 8.19

14. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Frequency of Mutation  Spontaneous mutation rate = 1 in 10 9 replicated base pairs or 1 in 10 6 replicated genes  Mutagens increase to 10 –5 or 10 –3 per replicated gene.

15. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Selection  Positive (direct) selection detects mutant cells because they grow or appear different.  Negative (indirect) selection detects mutant cells because they do not grow. PLAY Animation: Mutations and DNA Repair

16. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Genetic Transfer and Recombination  Vertical gene transfer: Occurs during reproduction between generations of cells.  Horizontal gene transfer: The transfer of genes between cells of the same generation. PLAY Animation: Horizontal Gene Transfer

17. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Transformation Figure 8.23

18. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Recombination Figure 8.24

19. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Conjugation Figure 8.26a

20. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Conjugation Figure 8.26b

21. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Conjugation PLAY Animation: Bacterial Conjugation Figure 8.26c

22. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Transduction Figure 8.27

23. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Plasmids  Conjugative plasmid: Carries genes for sex pili and transfer of the plasmid  Dissimilation plasmids: Encode enzymes for catabolism of unusual compounds  R factors: Encode antibiotic resistance

24. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Plasmids Figure 8.28

25. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Sensitive to DNase? a. b. c.

26. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings You have isolated a strain of E. coli that is resistant to penicillin, streptomycin, chloramphenicol, and tetracycline. You also observe that when you mix this strain with cells of E. coli that are sensitive to the four antibiotics, they become resistant to streptomycin, penicillin and chloramphenicol, but remain sensitive to tetracycline. Explain what is going on.