Sections of a Gene


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•  The promoter as an example of non-coding DNA with a function

A gene is a sequence of DNA which is transcribed into RNA and contains three main parts:


  • The non-coding sequence responsible for the initiation of transcription
  • The core promoter is typically located immediately upstream of the gene’s coding sequence
  • The promoter functions as a binding site for RNA polymerase (the enzyme responsible for transcription)
  • The binding of RNA polymerase to the promoter is mediated and controlled by an array of transcription factors in eukaryotes
  • These transcription factors bind to either proximal control elements (near the promoter) or distal control elements (at a distance)

Coding Sequence

  • After RNA polymerase has bound to the promoter, it causes the DNA strands to unwind and separate
  • The region of DNA that is transcribed by RNA polymerase is called the coding sequence


  • RNA polymerase will continue to transcribe the DNA until it reaches a terminator sequence
  • The mechanism for transcriptional termination differs between prokaryotes and eukaryotes

Sections of a Gene

sections of a gene

Antisense vs Sense

A gene (DNA) consists of two polynucleotide strands, but only one is transcribed into RNA

  • The antisense strand is the strand that is transcribed into RNA
    • Its sequence is complementary to the RNA sequence and will be the "DNA version” of the tRNA anticodon sequence
    • The antisense strand is also referred to as the template strand
  • The sense strand is the strand that is not transcribed into RNA
    • Its sequence will be the “DNA version” of the RNA sequence (i.e. identical except for T instead of U)
    • The sense strand is also referred to as the coding strand (because it is a DNA copy of the RNA sequence)

Either of the 2 polynucleotide strands may contain a gene, and hence the determination of sense and antisense is gene specific

Antisense vs Sense Strands

sense vs antisense