|The deoxyribonucleic acid, DNA, is a long chain of nucleotides which consist of (figure 1):||
Figure 1: A nucleotide.
Note: in a nucleotide, the atoms of the organic base are numbered 1, 2, ... and the atoms of the sugar, wether it is a deoxyribose like in DNA or a ribose like in RNA, are numbered 1', 2', 5'. Atoms in the sugar component of a nucleotide provide the link between the base and the phosphate group. The 1' carbon is attached to the 9 nitrogen of a purine, or the 1 nitrogen of a pyrimidine. The OH (hydroxyl) group on the 5' carbon is replaced by a bond to the phosphate group (ester bond).
DNA consists of two associated polynucleotide strands that wind together in a helical fashion. It is often described as a double helix.
Each polynucleotide is a linear polymer in which the monomers (deoxynucleotides), are linked together by means of phosphodiester bridges , or bonds. These bonds link the 3' carbon in the ribose of one deoxynucleotide to the 5' carbon in the ribose of the adjacent deoxynucleotide. This is illustrated in Figure 2 .
|Figure 2: A segment of a single nucleic acid chain : this is a clickable MAP . On the right, is shown the double helix of DNA which is the normal state of the molecule.|
deoxyadenylate (A) is in blue,
deoxythymidylate (T) is in green,
deoxyguanylate (G) is in red,
deoxycytidylate (C) is in orange,
Naming nucleosides and nucleotides:
|Adenine (A)||Guanine (G)||Cytosine (C)||Thymine (T)|
|The combination of a deoxyribose and a base constitutes a deoxynucleoside .||Deoxyadenosine||Deoxyguanosine||Deoxycytidine||Deoxythymidine|
|The combination of a phosphate, a deoxyribose and a base constitutes a deoxynucleotide.||Deoxyadenylate||Deoxyguanylate||Deoxycytidylate||Deoxythymidylate|
|D||Deoxyribo : the pentose does not have any oxygen in position 2. Compare a deoxyribose with a ribose .|
|N||Nucleic: these molecules were first found in the nucleus of the cell , before being found in mitochondria, chloroplasts (of plant cells), and in the cytoplasm of prokaryotes.|
|A||Acid: only two of the three acid groups of the phosphoric acid are used to form the DNA chain. The third one gives the phosphoribo-backbone an acidic property.|