Transcription is the process by which the information in DNA is copied into messenger RNA (mRNA) for protein production by the enzyme RNA polymerase. It is the first step of gene expression. During transcription, a DNA sequence is read by an RNA polymerase, which produces a complementary, antiparallel RNA strand called a primary transcript. Although transcription is performed by RNA Polymerase, the enzyme needs other proteins to produce the transcript. These factors are either associated directly with RNA Polymerase or add in building the actual transcription apparatus. The general term for these associated proteins is transcription factor. Transcription factor is any protein other than RNA Polymerase that is required for transcription