Estimation of IS flanking DNA likely to be resolved and missed. A. The maximum number of fragments likely to be resolved, m, can be estimated by plotting the number of bands observed against the genomic copy number. Only a finite number of bands can be visualized on a gel. Consequently, the likelihood that two amplified fragments comigrate increases with the number of IS copies in the genome. B. The number of amplified flanking sequences likely to be missed rapidly increases when 10 or more bands are visualized. Genomic digests with a single restriction enzyme should be restricted to IS elements with fewer than 10 copies per genome. Genomes with more than 10 copies of an IS element should be screened using high resolution agarose gels and/or using a second restriction enzyme to allow all IS copies to be identified.