Production of RNA according to the sequence of DNA.

Transcription and DNA replication are comparable, because DNA and RNA molecules are very similar to each other. For transcription, the DNA double helix is partially unwound into the single strands. One of the two strands is then used as a template for the production of the RNA molecule. Because of base pairing the sequence of the newly formed RNA molecule is complementary to the sequence of the DNA molecule (As one of the few differences, thymine (T) of DNA is replaced by uracil (U) in RNA. Accordingly, T corresponds to A, A corresponds to U, G corresponds to C, and C corresponds to G).