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Transcription is the copying of DNA into complementary mRNA.

Transcription is an important step in protein synthesis and occurs inside the nucleus. It can be broken down into three steps:

  1. Initiation: Enzymes such as RNA polymerase (RNAP) bind to the promoter region of the gene.

    A small section of the DNA is unwound, exposing the bases for transcription. Only one strand of the DNA is transcribed and used as a template for protein synthesis.

  2. Elongation: Complementary RNA nucleotides assemble alongside the DNA template. RNA polymerase catalyses the formation of phosphodiester bonds between the RNA nucleotides.

  3. Termination: Transcription ends when RNA polymerase reaches the terminator sequence, a section of non-coding DNA positioned just downstream of the gene.

    The terminator sequence causes the polymerase to unbind from the DNA. A single strand of mRNA is released.