Agarose gel electrophoresis following PCR with the tel 1 and tel 2 primers. PCR was as described in Materials and Methods, except that 22 cycles of PCR were performed instead of 18 cycles. Eight microliters of reaction product were then loaded into each lane of a 4% (Nusieve 3:1) agarose gel and electrophoresis carried out at ∼2.5 V/cm in 45 mM Tris–borate, 1 mM EDTA with ethidium bromide present at a concentration of 0.5 µg/ml. The gel was then transilluminated with UV light and digital photography was performed with the Stratagene EagleEye System. Lanes 1, 2, 8 and 9, size standards. For lane 3 the template for PCR was 35 ng of total human genomic DNA. The remaining samples differed from the lane 3 sample as follows: lane 4, no primers; lane 5, no polymerase; lane 6, E.coli genomic DNA as template instead of human genomic DNA; lane 7, no template. The bottom of the smear in lane 3 was estimated to contain a 76 bp product, based on a comparison of its mobility with the mobilities of the size standards in a plot of log(number of base pairs) versus distance migrated from the origin.