Ethidium bromide–stained gels showing quantitative competitive RT-PCR analysis of MTIIa induced after 8 hours of Cd2+, Cu2+, or Zn2+ treatment. RNA (300 ng) was amplified in the presence of increasing amounts (0–500 pg) of competing MTIIa mimic DNA. Indicated are the metal concentrations, the 237-bp MTIIa cDNA, the 99-bp MTIIa mimic DNA PCR products, and the calculated radioactivity incorporated in each PCR product.