Quantitative RT-PCR for the ATM transcript. A control EBV-transformed lymphoblast cell line (C3ABR) and 2 sets of freshly isolated PBMCs and PHA-stimulated PBMCs from healthy controls (1 and 2) were examined. Each template contained the same amounts of cDNA corresponding to 0.1 μg of total RNA and 1 of 2-fold dilutions of a competitor DNA from 1/2 × 10 to 1/256 × 10 attomole (lanes a through h). Equivalent points where target cDNA and competitor DNA were almost equivalent are indicated by arrow heads. The positions of target cDNA and competitor DNA (Comp.) are also indicated by arrows.