Book Viewer

Short Contents | Full Contents | Other books @ NCBI

| Modern Genetic Analysis Chapter 9. The Genetics of Bacteria and Phages Bacterial Gene Transfer in Review Figure 9-25. Recombination processes in bacteria. Bacterial recombination requires that a bacterial cell receive an allele obtained from another cell. (a) In conjugation, a cytoplasmic element such as the fertility factor (F) integrates into the chromosome of a bacterial cell. During cell-to-cell contact, the integrated factor can transfer part or all of that chromosome to another cell whose chromosome carries alleles of genes on the transferred chromosome. The transferred segment recombines with a homologous segment in the recipient cell's chromosome; in the example shown here, allele B thereby replaces allele b. (b) In transformation, a DNA segment bearing a particular allele is taken up from the environment by a cell whose chromosome carries a matching allele; the alleles (in our example, B and b) are then exchanged by homologous recombination. (c) In transduction, after a phage has infected a bacterial cell, one of the newly forming phage particles picks up a bacterial DNA segment instead of viral DNA. When this phage particle infects another cell, it injects its bacterial DNA, which recombines with a homologous segment in the second cell, thereby exchanging any corresponding alleles (in our example, A and a).

© 1999 by W. H. Freeman and Company. All rights reserved.