A schematic map of a plasmid with several insertions of simple and composite transposons carrying resistance genes. Plasmid sequences are in blue. Genes encoding resistance to the antibiotics tetracycline (tetR), kanamycin (AanR), streptomycin (smR), sulfonamide (suR), and ampicillin (ampR) and to mercury (hgR) are shown. The resistantdeterminant segment can move as a cluster of resistance genes. Tn3 is within Tn4. Each transposon can be transferred independently.
[Data from S. N. Cohen and J. A. Shapiro, “Transposable Genetic Elements.” Copyright 1980 by Scientific American, Inc. All rights reserved]