Figure 1. Diagrammatic representation of the TMDH process.

(A) A library of transposon mutants is obtained using a custom transposon with outward-facing T7 and SP6 promoters. Genomic DNA is extracted from the library and digested using a restriction endonuclease (RsaI). Labelled RNA run-offs are obtained from the T7 and SP6 promoters by in vitro transcription. (B) The labelled RNA run-offs are hybridised to genome-wide tiling microarrays. By examining the distribution of microarray signals between RsaI restriction sites (vertical black lines) it is possible to infer the location of the transposon (green triangle). Comparison of the library grown in vitro (input) with the library obtained after passage through a mouse (output) allows attenuating mutants to be identified, since they give lower signals in the output.