166 Chapter 5 • The Genetics of Bacteria and Their Viruses 5.3 Bacterial transformation Transformation as another type of bacterial gene transfer Some bacteria can take up fragments of DNA from the external medium. The source of the DNA can be other cells of the same species or cells of other species. In some cases the DNA has been released from dead cells; in other cases the DNA has been secreted from live bac-terial cells. The DNA taken up integrates into the recipi-ent’s chromosome. If this DNA is of a different geno-type from the recipient, the genotype of the recipient can become permanently changed, a process aptly termed transformation. Transformation was discovered in the bacterium Streptococcus pneumoniae in 1928 by Frederick Grif±th. In 1944, Oswald T. Avery, Colin M. MacLeod, and Maclyn McCarty demonstrated that the “transforming principle” was DNA. Both results are milestones in the elucidation of the molecular nature of genes. We con-sider this work in more detail in Chapter 7. The transforming DNA is incorporated into the bac-
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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.