Molecular analysis of rearrangements in human ribosomal RNA gene clones

Human placental DNA, enriched for ribosomal sequences, was cloned in the phage vector lambda Charon 16A. Recombinants containing 28S rDNA sequences were isolated, and all were found to have deletions in the insert and/or vector DNA. Electron microscopic analysis was used to map the deletions and provide evidence that unstable forms of the recombinants can revert to the original vector or undergo further rearrangements. Specific deletions are manifested as previously unreported plaque phenotypes.