Generalized Adaptor-Tagged Competitive PCR (GATC-PCR). (A) Gene-specific primer (GSP)-dependent amplification from Y-shaped adaptor-tagged template. (B) An example of GATC-PCR. Genomic DNA and cDNA digested with Mbo I were ligated with adaptor A/C and B/C (Table 2), respectively, and used for GATC-PCR. The products of four assays (blue, green, red, and black) and a size standard (orange) were separated on ABI 3730 Genetic Analyzer. The fast- and slow-migrating peaks of each pair correspond to the signals from genomic DNA and cDNA, respectively. (C) Linearity of GATC-PCR from genomic DNA templates. Genomic DNAs extracted from the wild and gcn4Δ cells were combined at appropriate ratios to prepare a series of genomic DNAs containing 0, 0.25, 0.5, 0.75, and 1 copy of GCN4 per haploid on average, digested with Mbo I, and ligated to the adaptors A/C and B/C (Table 2). Various combinations of the A/C- and B/C-tagged templates were mixed in a 1:1 ratio, while keeping the total amount equivalent to 3,000 haploid cells, and subjected to GATC-PCR using a GCN4-specific primer. (D) Linearity of GATC-PCR from cDNA templates. An experiment similar to the one shown in (C) was conducted using cDNAs, instead of genomic DNA, prepared from the wild and gcn4Δ cells.