Tandem copies of the transgene are arrayed head-to-tail at a single insert locus.

<p>(A) Schematic diagram of restriction enzyme sites and the sizes expected by Southern blot analysis. Bold lines show the position of the probe. B, <i>BamHI</i>; EI, <i>EcoRI</i>; S, <i>SalI</i>; Xb, <i>XbaI</i>; Xh, <i>XhoI</i>. (B) Southern blot analysis. Genomic DNA from <i>MYCN</i>^Tg/+ mouse was digested with indicated restriction enzymes. Note that all results are consistent with the expected size shown in (A). (C) Quantification of transgene copy number. Genomic DNA (5 µg per lane) from <i>MYCN</i>^Tg/+ and wild type mice were digested with <i>EcoRI</i> and <i>SalI</i>. Copy standards were prepared by mixing wild type DNA with a known amount of DNA and subjected to Southern blot analysis. <i>MYCN</i>^Tg/+ mouse has about 5–6 copies of the transgene.