Comparative Analysis of Invertible DNA in Phage Genomes

Invertible DNA has been found to be a particular kind of genetic controlling element that is capable of switching genetic information on and off. Two prototypes have been found thus far: the invertible hin function in Salmonella, which controls flagellar phase variation, and the invertible G segment of bacteriophage Mu, which is responsible for alternating host ranges of the phage (Silverman and Simon 1983). The invertible segments differ in their principal arrangements. The inversion in Salmonella moves a transcription signal so that genes outside the invertible element are turned on and off. The inversion function (hin) is part of the invertible DNA. In contrast, the genes that are regulated by inversion of the G segment are inside the invertible DNA, so that two sets of genetic information are alternately expressed via an outside promoter, and the inversion function (gin) is located adjacent to the invertible G segment.