text: rt-pcr gene expression? how is rt-pcr used to determine gene expression? how is gene expression determine with proteins? how is gene expression used to determine transcription?   thank you rt-pcr converts mrna to cdna, amplifies the cdna to determine the relative expression of a transcribed gene.  proteins can be measured by western blots or to a lesser extent immunocytochemistry. however, protein expression does not necessarily mean functional...  transcription can be measured by measuring mrna like in rt-pcr or northern blots.