Reverse Transcriptase - This enzyme uses an RNA molecule as template and synthesizes a DNA strand complementary to the RNA molecule.

These enzymes are used to synthesize the DNA from RNA. These enzymes are present in most of the RNA tumour viruses and retroviruses.

Reverse transcriptase enzyme is also called as RNA dependent DNA polymerase. Reverse transcriptase enzyme, after synthesizing the complementary strand at the 3 end of the DNA strand, adds a small extra nucleotide stretch without complementary sequence. This short stretch is called as R-loop.