DNA sequencing

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The sequence of nucleotides of isolated fragments of DNA can be deduced by at least two different groups of chemical reactions. The most famous of these methods are those of Sanger - the dideoxy technique - and Maxam & Gilbert - the cleavage technique. The latter technique is now outmoded.

The production of machines that can undertake these reactions repeatedly and at speed has added impetus to the Human Genome Project.

The Human Genome Project originally aimed to map the nucleotides contained in a human haploid reference genome (more than three billion)

  • the "genome" of any given individual is unique; mapping "the human genome" involves sequencing multiple variations of each gene
  • project did not study the entire DNA found in human cells; some heterochromatic areas (about 8% of the total genome) remain unsequenced
  • project got underway in 1990, and was declared complete in 2003


Last reviewed 01/2018