(last update : 09-11-1999)
What is DNA
- 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.
Figure 2 : The components of nucleotides. (pdf file of this picture)
How do the nucleotides form a DNA chain ?
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.
- dATP : deoxyadenosine triphosphate
- dGTP : deoxyguanosine triphosphate
- dTTP : deoxythymidine triphosphate
- dCTP : deoxycytidine triphosphate
back to homepage
Next : DNA in a cell