Reverse transcriptase (RT) is a DNA polymerase that is capable of utilizing an RNA template to create a complementary DNA sequence (cDNA). This activity is important for viruses that store their genetic information as RNA instead of as DNA. Reverse transcriptases are extremely useful molecular biology reagents because they permit the generation of DNA complements of RNA molecules of interest. This conversion allows researchers to manipulate DNA sequences that correspond to their RNAs of interest using standard DNA reagents. RT-PCR is a method of DNA amplification that begins with the transcription of mRNA into cDNA, followed by a series of step-wise temperature changes that allow the exponential replication of the cDNA molecule (PCR).