Introduction to Genetic Analysis 171

Introduction to Genetic Analysis 171 - 170 Chapter 5 •...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 170 Chapter 5 • The Genetics of Bacteria and Their Viruses made use of the fact that rII mutants will not infect a strain of E. coli called K. Therefore he made the rII 3 rII cross on another strain and then plated the phage lysate on a lawn of strain K. Only rII 1 recombi- nants will form plaques on this lawn. This way of finding a rare genetic event (in this case a recombinant) is a selective system: only the desired rare event can produce a certain visible outcome. Contrast this with screens, systems in which large numbers of individuals are visu- ally scanned to seek the rare “needle in the haystack.” This same approach can be used to map mutant sites within genes for any organism from which large numbers of cells can be obtained, and for which it is possible to easily distinguish wild-type and mutant phe- notypes. However, this sort of intragenic mapping has been largely superseded by the advent of cheap chemi- cal methods for DNA sequencing, which identify the positions of mutant sites directly. to hydrolytic enzymes. Thus, Lederberg and Zinder had discovered a new type of gene transfer, mediated by a virus. They were the first to call this process transduction . As a rarity in the lytic cycle, virus particles sometimes pick up bacterial genes and transfer them when they infect another host. Transduction has subse- quently been demonstrated in many bacteria.quently been demonstrated in many bacteria....
View Full Document

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.

Ask a homework question - tutors are online