Sequence homology in DNA molecules of temperate phages φ81, φ80 and λ

Summary

Homology maps between bacteriophages ϕ81, ϕ80 and λ were constructed on the basis of electron microscope observation of DNA heteroduplexes. In ϕ81/ϕ80 heteroduplex, the left half and the right terminal region of 13% the total molecular length were highly homologous, while the remaining region covering the early gene cluster was entirely nonhomologous. In ϕ81/λ heteroduplex, high-degree homologies were detected at the left 14% terminal region covering the head gene cluster, the central 3.8% region covering the att-int-xis region and the 1.3% Q homology region. Low-degree homologies of shorter length were scattered at the tail gene cluster, b2 region, cIII region, PQ region and SR region. Comparing our results with the homology maps of other lambdoid phages reported by Simon et al. (1971) and Fiandt et al. (1971), a phylogenic relation of ϕ81 to other lambdoid phages and the role of recombination in the course of divergence of lambdoid phages are discussed.