Transcription is the process by which an RNA sequence is produced from a DNA template

• Transcription is mediated by the enzyme RNA polymerase, which separates the DNA strands by breaking the hydrogen bonds between the base pairs
  

• While the DNA strands are separated, free nucleotides align opposite their exposed complementary base partner
  

• RNA polymerase then covalently joins the free nucleotides together (5’ → 3’) to generate an RNA transcript of the DNA sequence
  

• Once the RNA sequence has been synthesised, RNA polymerase detaches from the DNA molecule and the double helix reforms
  

Transcription Animation

Sense versus Antisense

The segment of double-stranded DNA that codes for an RNA sequence is called a gene – but only one strand is actually transcribed

• The strand that is transcribed is called the template strand and is complementary in sequence to the RNA transcript (it is ‘antisense')
  

• The strand that is not transcribed is called the coding strand and is identical in sequence to the RNA transcript (it is ‘sense')
  

  • The only difference between the transcript and the coding strand is that RNA uses uracil instead of thymine