# RNA Polymerase --- **RNA polymerase** is a class of [[enzyme]] complex that catalyzees the [[transcription]] of RNA. In other words, it catalyzes the polymerization of ribonucleotides. RNA polymerase uses [[DNA]] as a template, and unlike *DNA* polyermase, does not require a [[DNA replication#Step 2 Laying The RNA Primer|primer]] (it can start the process from a free hydroxyl group on a tyrosine residue). Additionally It can unzip the strand on it's own, and lets them join back up afterwards. ![[RNA polymerase.png]] ## Function RNA polymerase must first find the correct [[transcription|promoter]] for the gene it wants to transcribe. In bacteria it does this with the help of [[sigma factor]]. Then, after latching on and (temporarily) unzipping the DNA strands, it has to chose which [[DNA#Strands|strand]] to transcribe (which is the non-coding, or "template" strand). ## Reverse Transcriptase **Reverse transcriptase** is basically does the opposite of RNA polymerase and converts [[RNA]] into [[DNA]]. First taken from [[virus|retroviruses]], but now very useful in the field of biotechnology. It's important because they allow us to purify mature, and decode the proteins that are found in the DNA. Put simply, RT allows us to convert mRNA to DNA, which we can then take and put into a plasmid with the help of some DNA polymerase and ligase. ___