Introduction to Genetic Analysis 169

Introduction to - 44200_05_p151-184 10:47 AM Page 168 168 Chapter 5 The Genetics of Bacteria and Their Viruses Clear areas or plaques Uninfected

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168 Chapter 5 The Genetics of Bacteria and Their Viruses microscope? In this case, we cannot produce a visible colony by plating, but we can produce a visible manifes- tation of a phage by taking advantage of several phage characters. Let’s look at the consequences of a phage’s infecting a single bacterial cell. Figure 5-23 shows the sequence of events in the infectious cycle that leads to the release of progeny phages from the lysed cell. After lysis, the progeny phages infect neighboring bacteria. Repetition of this cycle through progressive rounds of infection results in an exponential increase in the number of lysed cells. Within 15 hours after one sin- gle phage particle infects a single bacterial cell, the effects are visible to the naked eye as a clear area, or plaque, in the opaque lawn of bacteria covering the sur- face of a plate of solid medium (Figure 5-24). Such plaques can be large or small, fuzzy or sharp, and so forth, depending on the phage genotype. Thus, plaque
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.

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