RNA polymerase molecules are these biological catalysts that are used by our cells to basically synthesize RNA molecules from DNA molecules. So this process is called transcription. And in transcription we basically copy the genetic information found in the DNA onto the RNA molecule and then it's the RNA molecule that is used in a variety of different ways to basically synthesize the proteins that are needed for the survival of that cell. Now, we know that DNA molecules are very long molecules. They consist of many, many nucleotides. The question is how exactly does the RNA polymerase know where to begin the process of transcription on that DNA molecule?