I have a problem with my PCRs. From rat liver I have isolated total RNA, then synthesized cDNA with oligoDT primer. After that I used primers for PPARa and PPARb, ERa and ERb for my PCR using also primers for GAPDH as my reference gene. After the PCR my electroforesis in 2% agarose showed clear bands only for GAPDH. This means I guess that my technique is ok and my cDNA good but shouldn't I also see bands for all of my genes since in liver from bibliography all of them are expressed? I have tried it so many times, also with new primers, but the result keeps the same.