ABSTRACT
The polymerase chain reaction (PCR) technique was developed to amplify, with high efficiency, double-stranded or single-stranded deoxyribonucleic acid (DNA) sequences. Amplification of individual Ribonucleic acid (RNA) molecules can also be accomplished with PCR when coupled with reverse transcription (RT) of RNA into a complementary DNA (cDNA) copy. A number of methods such as Northern blots, RT-PCR, RNase protection assays, in situ hybridization, dot blots and SI nuclease assays have been developed to measure gene expression in different tissues and cells. RNA sequences are amplified by the use of combined cDNA and PCR methods. The RT-PCR method is a highly sensitive tool in the study of gene expression at the RNA level in mammalian tissues. Exogenous sequences are also used as templates in competitive PCR and share the same primer annealing sequences as the target nucleic acids and thus compete for the same primers and for amplification.
