Genetic mapping of the inversion loop in bacteriophage Mu DNA.

An inversion loop seen in heteroduplex mapping of the DNA of mature Mu phage induced from a lysogen is observed also in defective lambda phage carrying one end of Mu. 14% of the DNA of Mu, including this region, designated the G loop, is shown to be to the right of all known genes in the prophage map. The inhomogeneous ends of Mu are observed as a separate phenomenon and appear in all mutants investigated. The recA and recBC functions of the host are not needed for the inversion responsible for the G loop to take place. Deletions of Mu DNA in the G-loop region have been isolated and are under study.