(last update : 09-11-1999)

What is DNA

  1. Nucleotides are the building stones of DNA.

    There are 4 different nucleotides :

    For convenience, these 4 nucleotides are called dNTP's (deoxynucleoside triphosphates). A nucleotide is made of three major parts : a nitrogen base, a sugar molecule and a triphosphate. Only the nitrogen base is different in the 4 nucleotides.

    The nucleotides

    Figure 2 : The components of nucleotides. (pdf file of this picture)

  2. How do the nucleotides form a DNA chain ?

    DNA

    Figure 3 : From nucleotide to DNA. (pdf file of this picture)

    DNA is formed by coupling the nucleotides between the phosphate group from a nucleotide (which is positioned on the 5th C-atom of the sugar molecule) with the hydroxyl on the 3rd C-atom on the sugar molecule of the previous nucleotide. To accomplish this, a diphosphate molecule is split off (and releases energy). This means that new nucleotides are always added on the 3' side of the chain.
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