Transcription in biology is the process of making an RNA copy of a DNA sequence, usually to produce messenger RNA (mRNA) that can be used to build proteins. It occurs where the DNA is located: in the nucleus of eukaryotic cells and in the cytoplasm of prokaryotic cells.

What transcription is

  • Transcription uses DNA as a template to build an RNA molecule whose base sequence is complementary to one DNA strand.
  • The enzyme RNA polymerase binds to DNA, unwinds a small region (a “transcription bubble”), and links RNA nucleotides together to form mRNA.

Where it occurs

  • In eukaryotes (like human cells), transcription happens in the nucleus, because that is where chromosomal DNA is stored.
  • In prokaryotes (like bacteria), there is no membrane-bound nucleus, so transcription happens directly in the cytoplasm, where the DNA sits.

Why it matters

  • mRNA produced by transcription carries genetic information from DNA to ribosomes, where translation uses that information to make proteins.
  • In eukaryotes, transcription (in the nucleus) and translation (in the cytoplasm on ribosomes) are separated in space and time, while in many bacteria they can even happen at the same time on the same mRNA.

TL;DR: Transcription is copying DNA into RNA (usually mRNA), and it occurs in the nucleus of eukaryotes and in the cytoplasm of prokaryotes.