Comprehension Questions

Section 9.1

Question 9.1

Explain how auxotrophic bacteria are isolated.

Question 9.2

What is the difference between complete medium and minimal medium? How are complete media and minimal media to which has been added one or more nutrients (supplemental media) used to isolate auxotrophic mutants of bacteria?

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Section 9.2

Question 9.3

Briefly explain the differences between F+, F−, Hfr, and F′ cells.

Question 9.4

What types of matings are possible between F+, F−, Hfr, and F′ cells? What outcomes do these matings produce? What is the role of F factor in conjugation?

Question 9.5

Explain how interrupted conjugation, transformation, and transduction can be used to map bacterial genes. How are these methods similar and how are they different?

Question 9.6

What is horizontal gene transfer and how might it take place?

Section 9.2

Question 9.7

List some of the characteristics that make bacteria and viruses ideal organisms for many types of genetic studies.

Question 9.8

What types of genomes do viruses have?

Question 9.9

Briefly describe the differences between the lytic cycle of virulent phages and the lysogenic cycle of temperate phages.

Question 9.10

Briefly explain how genes in phages are mapped.

Question 9.11

How does specialized transduction differ from generalized transduction?

Question 9.12

Briefly explain the method used by Benzer to determine whether two different mutations occurred at the same locus.

Question 9.13

Briefly describe the genetic structure of a typical retrovirus.

Question 9.14

Explain how a retrovirus, which has an RNA genome, is able to integrate its genetic material into that of a host having a DNA genome.

Question 9.15

What are the evolutionary origins of HIV-1 and HIV-2?

Question 9.16

Most humans are not easily infected by avian influenza. How then do DNA sequences from avian influenza become incorporated into human influenza?

For more questions that test your comprehension of the key chapter concepts, go to for this chapter.