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Modern Genetic Analysis
9. The Genetics of Bacteria and Phages
Key Concepts

Some E. coli cells carry a circular plasmid called the sex factor, F.
Factor F can exist in a free state in the cytoplasm or it can be integrated into the circular bacterial chromosome.
In the nonintegrated state, F can pass into F-free cells during cell conjugation.
When F is integrated, the bacterial chromosome is transferred linearly to an F-free cell during conjugation.
Bacteriophages can transfer (transduce) DNA from one bacterial cell to another.
During generalized transduction, random chromo-some fragments are incorporated into the heads of phages and transferred to other cells by infection.
During specialized transduction, specific genes near the phage-integration sites on the bacterial chromosome are mistakenly incorporated into the phage genome and transferred to other cells by infection.
DNA from the medium can enter a bacterial cell and integrate into the chromosome, thereby transforming the genotype.
The different methods of gene transfer in bacteria generate partial diploids that permit the study of recombination and gene interaction.

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