Genes are a specific sequences of DNA located on the chromosomes.

Chromosomes consist of proteins (histones) combined with two complementary chains of DNA.

Two chromosome strands are arranged in a spiral known as the double helix.

Photograph of a model of a DNA double helix

A gene can be described as a linear piece of DNA that includes:

  • a regulatory sequence that determines when the gene will be transcribed
  • an initiation sequence
  • exons that are the coding region
  • introns that are non coding regions and are spliced out of the gene during transcription
  • a termination sequence

Diagram of a gene that illustrates the sequence described in the text.