Q-PCR validation of SAGE results. Quantitative comparisons of transcript levels in larval CNS RNA from RU486 treated (hepact induced) versus control samples. Values represent average cycle difference in PCR product between induced and control samples (N = 5). Each cycle change corresponds to a 2-fold difference in mRNA levels (see Methods). After induction of hepact, hep RNA levels increase 16-fold relative to control (P < 0.001); puc RNA, not identified by SAGE, is induced three-fold relative to control (P < 0.01). While SAGE targets appl and cher show induction above control RNA levels, white is induced more than 32-fold (P < 0.001).