Electron-microscopic visualization of deletion mutations

Deletion mutants of λ coliphage were discovered by Kellenberger, Zichichi, and Weigle.(1) The deletions can be mapped by genetic recombination experiments. It is not known if the recombination maps thus obtained give the true physical position of the deletions. The present paper describes a method for mapping deletion mutations with the electron microscope, thus obtaining the physical position of the deletion.