Shared genetic modules of the T12-related prophage family. The top line is the simplified genetic map of bacteriophage T12 colored by gene or genetic module for the integrase, repressor-antirepressor, DNA replication, DNA modification, DNA packaging, capsid proteins, lysis, and virulence (speA). Regions of unknown or uncertain function are colored gray. Beneath T12 is shown the genetic maps of the other genome prophages that share the extended region dedicated to packaging, capsid proteins, and lysis. DNA regions that are divergent from T12 are not shown. The figure illustrates that a structural gene module can be associated with divergent attachment sites or virulence genes. The alignment was derived from the phylogenetic tree presented in Fig. 5.