April 2010
Written by Hana Kucera

Transcription is the first step in converting the information stored on chromosomes into proteins. During transcription, the DNA is read and a messenger RNA molecule is made. First, an enzyme called RNA polymerase attaches to the DNA molecule that will act as the template. The RNA polymerase binds to the DNA molecule just in front of the start of the gene and separates the two strands of DNA. RNA polymerase then travels along the DNA strand using it to make a complementary copy of RNA. Remember that RNA uses the nucleotide uracil in place of thymine.

Transcription can be used to make multiple copies of the same gene. Many RNA polymerases can read and transcribe a single DNA strand at the same time, producing many mRNAs.

Transcription is also used to produce ribosomal RNA and transfer RNA or enzymes made of RNA and in these cases, the products of transcription do not go on to translation into protein, but can carry out their functions while remaining RNA molecules.

In eukaryotes, transcription (as well as post-transcriptional processing) occurs in the nucleus, and the final mRNA messages are transported out to the cytoplasm to be translated into protein.

For an overview of how Transcription fits in the process of making proteins, see here