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Genetic Information in Bacterial Cells

Genetic Information in Bacterial Cells . 1. Bacterial Reproduction: Binary Fission . Bacterial chromosome and Plasmids to each. 2. Types of Gene Transfer in Bacterial Cells . Transformation - ‘naked’ DNA fragments from donor to recipient

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Genetic Information in Bacterial Cells

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  1. Genetic Information in Bacterial Cells 1

  2. Bacterial Reproduction: Binary Fission Bacterial chromosome and Plasmids to each 2

  3. Types of Gene Transfer in Bacterial Cells Transformation - ‘naked’ DNA fragments from donor to recipient Transduction - Virus carries DNA fragment from donor to recipient Conjugation - Cell : Cell contact required Donor cell: F +, Hfr Recipient: F - 3

  4. Gene Transfer in Bacteria Linear or circular DNA is transferred 4

  5. Transformation DNA from disrupted donor Homologous Recombination Double CO Heteroduplex DNA replication Closely linked genes cointegrate Transformant with new phenotype 5

  6. Transformation: Determining Gene Order Would you see p+ q o+ transformants? 6

  7. Transformation: Determining Gene Order Least frequent, so a-b far apart a-c closer together b-c closer together Therefore a - c - b Sample problem 7

  8. Transduction: Life Cycle of Phage  Lytic or Lysogenic 8

  9. Transduction: Generalized Fragments of bacterial chromosome randomly packaged into phage 9

  10. Transduction: Generalized Integration requires DCO Cotransduction indicates linkage 10

  11. Transduction: Specialized Phage integrates Takes specific gene with it during excision 11

  12. Conjugation Lederberg & Tatum (1946) Davis (1946) Cell contact required 12

  13. Conjugation Sex pilus (F-pilus) F+ cells F factor - plasmid 13

  14. Conjugation: F+ x F- mating F factor nicked at origin Rolling circle replication Linear transfer of genes 5 4 3 2 1 F Recipient becomes F+ 14

  15. Conjugation: Origin of Hfr cells F factor integrates a b p c m p m c b a 15

  16. Conjugation: Hfr x F-cells New genes must integrate into bacterial chromosome Trans-conjugant still F- 16

  17. Conjugation: Transfer of Genes from Hfr Cell Genes transferred in order Minute mapping possible 17

  18. Conjugation: Transfer of Genes from Hfr Cell Minute Mapping 18

  19. Conjugation: Interrupted-Mating with Hfr Strains Determine gene order, position and orientation of F factors 19

  20. Conjugation: Sample Problem Hfr Mapping Indicate positon of each gene, each F-factor, and orientation 20

  21. Conjugation: Determining Gene Order Also applicable to Transformation and Transduction 21

  22. Conjugation: Determining Gene Order 22

  23. Conjugation: Determining Gene Order Order is d-f-e or e-f-d 23

  24. Conjugation: Origin of F’ Strains F’ cell Transfers specific genes Recipient - merozygote partial diploid 24

  25. Genetic Analysis of Viruses Viruses - small genome, rapid reproduction large numbers enable mapping within genes (1 in 1012 recombinants observed) 25

  26. Benzer’s Experiments: T4 bacteriophage Wild type Rapid lysis (rII) mutants Small rough plaques Large round plaques Grow in E. coli Grow in E. coli Strains B and K12 Strain B , NOT K12 26

  27. Benzer’s Experiments: T4 bacteriophage Complementation tests with numerous rII mutants K12 K12 27

  28. Benzer’s Experiments: T4 bacteriophage Intragenic mapping of independently isolated rIIA mutants E.coli B Transfer to strain K12 to select for wild-type recombinants Frequency = distance between different mutation 28

  29. Deletion Mapping Facilitates mapping of mutations If mutation is in region of deletion, no wild-type recombinants occur. If mutation is in different region, wild-type recombinants will occur. 29

  30. Deletion Mapping: Sample Problem 1 Locations of deletions (white) and DNA ( ) Where is a3 located? 30

  31. Deletion Mapping: Sample Problem 2 Line represents deletion, intact DNA is not shown Where is a3 located? 31

  32. Deletion Mapping: Complete map of rII locus Locations of 32

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