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Copyright © 2009 Pearson Education, Inc. PowerPoint ® Lecture Presentation for Concepts of Genetics Ninth Edition Klug, Cummings, Spencer, Palladino Chapter.

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Presentation on theme: "Copyright © 2009 Pearson Education, Inc. PowerPoint ® Lecture Presentation for Concepts of Genetics Ninth Edition Klug, Cummings, Spencer, Palladino Chapter."— Presentation transcript:

1 Copyright © 2009 Pearson Education, Inc. PowerPoint ® Lecture Presentation for Concepts of Genetics Ninth Edition Klug, Cummings, Spencer, Palladino Chapter 6 Genetic Analysis and Mapping in Bacteria and Bacteriophages Lectures by David Kass with contributions from John C. Osterman. Copyright © 2009 Pearson Education, Inc.

2 Section 6.1 6.1Bacteria Mutate Spontaneously and Grow at an Exponential Rate Spontaneous mutation that occurs in the presence or absence of phage is considered the primary source of genetic variation in bacteria.

3 Copyright © 2009 Pearson Education, Inc. Section 6.1 Selection is the growth of the organism under conditions in which only the mutant of interest grows well, whereas the wild type does not.

4 Copyright © 2009 Pearson Education, Inc. Section 6.1 Prototroph can synthesize all essential organic compounds, and therefore can be grown on minimal medium. Auxotroph through mutation, has lost the ability to synthesize one or more essential compounds, and must be provided with them in the medium if it is to grow.

5 Copyright © 2009 Pearson Education, Inc. Section 6.1 Bacteria have 4 phases when grown in culture: lag phase log phase (exponential growth) stationary phase death phase

6 Copyright © 2009 Pearson Education, Inc. microvet.arizona.edu

7 Copyright © 2009 Pearson Education, Inc. Section 6.2 6.2Conjugation Is One Means of Genetic Recombination in Bacteria Bacteria undergo conjugation, in which genetic information from one bacterium is transferred to another it recombines with the second bacteriums DNA

8 Copyright © 2009 Pearson Education, Inc. Figure 6.5

9 Copyright © 2009 Pearson Education, Inc. Section 6.2 In bacterial conjugation in E. coli, F + cells serve as DNA donors and F – cells are the recipients (Figure 6.6). F + cells contain a fertility factor (F factor) that confers the ability to donate DNA during conjugation. Recipient cells are converted to F +.

10 Copyright © 2009 Pearson Education, Inc. Figure 6.6

11 Copyright © 2009 Pearson Education, Inc. Section 6.2 An Hfr (high-frequency recombination) strain has the F factor integrated. An Hfr strain can donate genetic information to an F – cell, but the recipient does not become F +.

12 Copyright © 2009 Pearson Education, Inc. Section 6.2 Interrupted matings demonstrated that specific genes in an Hfr strain are transferred and recombined sooner than others (Figure 6.7).

13 Copyright © 2009 Pearson Education, Inc. Figure 6.7

14 Copyright © 2009 Pearson Education, Inc. Figure 6.8

15 Copyright © 2009 Pearson Education, Inc. Figure 6.9

16 Copyright © 2009 Pearson Education, Inc. Figure 6.10

17 Copyright © 2009 Pearson Education, Inc. Section 6.2 In some cases, an F factor is excised from the chromosome of an Hfr strain. In the process, the F factor (referred to as F) often brings several adjoining genes with it (Figure 6.11). Transfer of an F to an F – cell results in a partially diploid cell called a merozygote.

18 Copyright © 2009 Pearson Education, Inc. Figure 6.11

19 Copyright © 2009 Pearson Education, Inc. Section 6.4 6.4The F Factor Is an Example of a Plasmid Plasmids contain one or more genes and replicate independently of the bacterial chromosome (Figure 6.12).

20 Copyright © 2009 Pearson Education, Inc. Figure 6.12

21 Copyright © 2009 Pearson Education, Inc. Section 6.4 F factors confer fertility. R plasmids confer antibiotic resistance. Col plasmids encode colicins that can kill neighboring bacteria.

22 Copyright © 2009 Pearson Education, Inc. Section 6.5 6.5Transformation Is Another Process Leading to Genetic Recombination in Bacteria In transformation, small pieces of extracellular DNA are taken up by a living bacterial cell and integrated stably into the chromosome (Figure 6.13).

23 Copyright © 2009 Pearson Education, Inc. Figure 6.13

24 Copyright © 2009 Pearson Education, Inc. Section 6.6 6.6Bacteriophages Are Bacterial Viruses Bacteriophages can infect a host bacterium by injecting their DNA. Transduction Type of bacterial genetic recombination caused by the infection of a bacteriophage

25 Copyright © 2009 Pearson Education, Inc. Figure 6.14

26 Copyright © 2009 Pearson Education, Inc. Figure 6.15

27 Copyright © 2009 Pearson Education, Inc. Section 6.6 Lysogeny occurs when: the phage DNA integrates into the bacterial chromosome it is replicated along with the chromosome it is passed to daughter cells Bacteria containing a prophage are lysogenic and can grow and divide stably until viral reproduction is induced.

28 Copyright © 2009 Pearson Education, Inc. Section 6.7 6.7Transduction Is Virus-Mediated Bacterial DNA Transfer Bacteriophages, which can themselves undergo genetic recombination, can be involved in a mode of bacterial genetic recombination called transduction.

29 Copyright © 2009 Pearson Education, Inc. Section 6.7 The Lederberg-Zinder experiment led to the discovery of phage transduction in bacteria (Figure 6.17).

30 Copyright © 2009 Pearson Education, Inc. Figure 6.17

31 Copyright © 2009 Pearson Education, Inc. Figure 6.18

32 Copyright © 2009 Pearson Education, Inc. Section 6.7 In generalized transduction, bacterial DNA instead of phage DNA is packaged in a phage particle and transferred to a recipient host (Figure 6.18). In specialized transduction, a small piece of bacterial DNA is packaged along with the phage DNA.

33 Copyright © 2009 Pearson Education, Inc. Section 6.8 6.8Bacteriophages Undergo Intergenic Recombination Phage mutations often affect plaque morphology (Figure 6.19 and Table 6.1). Such mutations have been important in understanding genetic phenomena in phages.

34 Copyright © 2009 Pearson Education, Inc. Figure 6.19

35 Copyright © 2009 Pearson Education, Inc. Section 6.8 Mapping in Bacteriophages Mixed infection experiments demonstrated that intergenic recombination occurs in bacteriophages.

36 Copyright © 2009 Pearson Education, Inc. 6.9Intragenic Recombination Occurs in Phage T4 Seymour Benzers (1950s) detailed examination of the rII locus of phage T4 allowed him to produce a genetic map of this locus. Section 6.9

37 Copyright © 2009 Pearson Education, Inc. The End


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