Introduction to Genetic Analysis 172

Introduction to - E coli determined by P1 cotransduction The numbers given are the averages in percent for cotransduction frequencies obtained in

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171 5.5 Transduction a single piece of DNA. For example, suppose that we wanted to ±nd the linkage between met and arg in E. coli. We could grow phage P1 on a donor met 1 arg 1 strain, and then allow P1 phages from lysis of this strain to infect a met 2 arg 2 strain. First, one donor allele is se- lected, say, met 1 . Then, the percentage of met 1 colonies Donor bacterium a + + b + + + + + + Phages carrying donor genes + Recipient bacterium + Transduced bacterium + Figure 5-27 The mechanism of generalized transduction. In reality, only a very small minority of phage progeny (1 in 10,000) carry donor genes. 2.8 42, 40 68, 74 70 65, 66 21, 16 2.0 35 5.1, 5.0 (77), 13 (70), 46 purB hemA narC galU tonB cysB trp supF, C att f 80 Figure 5-28 Genetic map of the purB -to- cysB region of
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Unformatted text preview: E. coli determined by P1 cotransduction. The numbers given are the averages in percent for cotransduction frequencies obtained in several experiments. The values in parentheses are considered unreliable. [After J. R. Guest, Molecular and General Genetics 105, 1969, 285.] that is also arg 1 is measured. Strains transduced to both met 1 and arg 1 are called cotransductants. The greater the cotransduction frequency, the closer two genetic markers must be (the opposite of most mapping correlations). Linkage values are usually expressed as cotransduction frequencies (Figure 5-28). 44200_05_p151-184 3/4/04 10:47 AM Page 171...
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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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