Recall of the biosynthesis of DNA and the RNA

The desoxyribonucleic acid (DNA), which with basic proteins or histones form chromosomes, is the holder of biological information. Its replication allows the reproduction of the species, its transcription cellular operation via the protein synthesis, enzymes, conveyers, receiving etc

The enzymes necessary to the synthesis of DNA starting from the molecules provided by the external medium themselves are synthesized under the control of DNA, relayed by the ribonucleic acid (RNA).

The bacteria have two nucleic acids DNA and RNA, whereas the viruses have only one of them, either DNA, or the RNA.

The components of the ribonucleic acids and desoxyribonucleic are a purine base (adénine, guanine) or pyrimidic (cytosine, thymine, uracil), a sugar or dares (either D-ribose, or D-déoxyribose) and one, two or three molecules of phosphoric acid. The base + sugar constitute the ribonucléosides (adenosine, guanosine, cytidine and uridine) and the désoxyribonucléosides (désoxyadénosine, désoxyguanosine, désoxycytidine and désoxythymidine). Once phosphoryls, the nucleosides are called ribonucléotides and désoxyribonucléotides (we use indifferently the terms “désoxy” and “déoxy” indicated by the letter d).

On the pharmacological level, one inhibits the development of the micro-organisms (bacteria, virus, plasmodium) and of the tumors by disturbing the synthesis of DNA or RNA. One obtains this result while acting on two levels:

* Inhibition of the synthesis of the ribonucléotides and the déoxyribonucléotides (first biochemical stages leading to the synthesis of the RNA and DNA)
* Inhibition of the formation of DNA and functional RNA starting from the nucleosides (last stages of the synthesis). This inhibition is currently generally obtained by the administration of structural analogues either of the purine or pyrimidic bases or of the ribonucléosides or the déoxyribonucléosides, often called antimétabolites.
The biosynthesis of DNA and the RNA is a complex phenomenon bringing into play a great number of reactions and outcome at formed nucleotides of a purine or pyrimidic core and of a sugar, ribose or déoxyribose, dependant on phosphates groups.