The cloning of expressed genes involves the synthesis of DNA from mRNA using an enzyme called reverse transcriptase. Reverse transcriptase includes reverse transcriptase and a proprietary buffer designed for robust, reliable cDNA synthesis from a full range of rare and abundant transcripts. The synthesis of DNA from an RNA template, via reverse transcription, produces complementary DNA (cDNA). Reverse transcriptase uses an RNA template and a short primer complementary to the 3' end of the RNA to direct the synthesis of the first-strand cDNA, which can be used directly as a template for the polymerase chain reaction (PCR). This combination of reverse transcription and PCR (RT-PCR) allows the detection of low abundance RNAs in a sample, and production of the corresponding cDNA, thereby facilitating the cloning of low copy genes.