Transcription is the process by which the genetic information in DNA is converted into RNA. The mechanism of transcription can be described simply in 6 steps (5 in prokaryotes):
- The section of DNA to be transcribed is recognized by proteins involved in transcription.
- Hydrogen bonds between base pairs of DNA are broken and the DNA double helix "unzips."
- Complimentary RNA bases bind to the now exposed DNA bases
- RNA Polymerase binds the RNA bases together to form a strand of mRNA
- Hydrogen bonds formed between the original DNA strand and the new RNA strand are broken
- in eukaryotes, the new RNA strand is further processed and moves to the cytoplasm.
The segment of DNA to be transcribed is called a transcription unit, and contains at least one gene. If this gene codes for a protein, the RNA transcription product is called Messenger RNA, or mRNA. The gene may also code for Rybosomal RNA (rRNA), transfer RNA (tRNA), or a ribozyme.