1. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Lecture prepared by Mindy Miller-Kittrell, University of Tennessee, Knoxville M I C R O B I O L O G Y WITH DISEASES BY BODY SYSTEM SECOND EDITION Chapter 7 Microbial Genetics

2. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings The Structure and Replication of Genomes The Structure of Prokaryotic Genomes – Prokaryotic chromosomes – Main portion of DNA, along with associated proteins and RNA, packaged in 1-2 distinct chromosomes – Prokaryotic cells have a single copy of each chromosome (haploid) – Typical chromosome – circular molecule of DNA in nucleoid

3. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings The Structure and Replication of Genomes [INSERT FIGURE 7.2]

4. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings The Structure and Replication of Genomes The Structure of Prokaryotic Genomes – Plasmids – Small molecules of DNA that replicate independently – Carry information required for their own replication, and often for one or more cellular traits – Not essential for normal metabolism, growth, or reproduction – Can confer survival advantages – Many types of plasmids – Fertility factors – Resistance factors – Bacteriocin factors – Virulence plasmids – Cryptic plasmids

5. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings The Structure and Replication of Genomes The Structure of Eukaryotic Genomes – Nuclear chromosomes – Typically have more than one chromosome per cell – Chromosomes are linear and sequestered within membrane- bound nucleus – Eukaryotic cells often have two copies of each chromosome (diploid)

6. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings The Structure and Replication of Genomes [INSERT FIGURE 7.3]

7. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings The Structure and Replication of Genomes [INSERT TABLE 7.1]

8. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Gene Function [INSERT FIGURE 7.14]

9. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Gene Function [INSERT FIGURE 7.15]

10. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Gene Function Regulation of Genetic Expression – Nature of prokaryotic operons – An operon consists of a promoter and a series of genes – Some operons are controlled by a regulatory element called an operator

11. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Gene Function [INSERT FIGURE 7.19]

12. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Gene Function Regulation of Genetic Expression – Nature of prokaryotic operons – Inducible operons must be activated by inducers – Lactose operon – Repressible operons are transcribed continually until deactivated by repressors – Tryptophan operon

13. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Gene Function [INSERT FIGURE 7.20]

14. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Gene Function [INSERT FIGURE 7.21]

15. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Gene Function [INSERT TABLE 7.4]

16. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Mutations of Genes Mutation – change in the nucleotide base sequence of a genome Rare event Almost always deleterious Rarely leads to a protein having a novel property that improves ability of organism and its descendents to survive and reproduce

17. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Mutations of Genes Mutagens – Radiation – Ionizing radiation – induces breaks in chromosomes – Nonionizing radiation – induces pyrimidine dimers – Chemical Mutagens – Nucleotide analogs – disrupt DNA and RNA replication and cause point mutations – Nucleotide-altering chemicals – result in base-pair substitution mutations and missense mutations – Frameshift mutagens – result in nonsense mutations

18. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Mutations of Genes [INSERT FIGURE 7.23]

19. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Mutations of Genes [INSERT FIGURE 7.25]

20. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Mutations of Genes Frequency of Mutation – Mutations are rare events, otherwise organisms could not effectively reproduce themselves – Mutagens increase the mutation rate by a factor of 10 to 1000 times

21. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Genetic Recombination and Transfer Exchange of nucleotide sequences often mediated by DNA segments composed of homologous sequences Recombinants – cells with DNA molecules that contain new nucleotide sequences Vertical gene transfer – organisms replicate their genomes and provide copies to descendants

22. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Genetic Recombination and Transfer [INSERT FIGURE 7.30]

23. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Genetic Recombination and Transfer Horizontal Gene Transfer Among Prokaryotes – Horizontal gene transfer – donor cell contributes part of genome to recipient cell – Three types – Transformation – Transduction – Bacterial conjugation

24. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Genetic Recombination and Transfer Horizontal Gene Transfer Among Prokaryotes – Transformation – Transforming agent was DNA; one of conclusive pieces of proof that DNA is genetic material – Cells that take up DNA are competent; results from alterations in cell wall and cytoplasmic membrane that allow DNA to enter cell

25. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Genetic Recombination and Transfer [INSERT FIGURE 7.31]

26. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Genetic Recombination and Transfer Horizontal Gene Transfer Among Prokaryotes – Transduction – Generalized transduction – transducing phage carries random DNA segment from donor to recipient – Specialized transduction – only certain donor DNA sequences are transferred

27. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Genetic Recombination and Transfer [INSERT FIGURE 7.32]

28. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Genetic Recombination and Transfer [INSERT FIGURE 7.33]

29. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Genetic Recombination and Transfer [INSERT FIGURE 7.34]

30. Copyright © 2009 Pearson Education Inc., publishing as Pearson Benjamin Cummings Genetic Recombination and Transfer [INSERT TABLE 7.6]