Nucleoside triphosphates (NTP) are nucleosides with three phosphates . Natural nucleoside triphosphates are represented by adenosine triphosphate (ATP), guanosine triphosphate (GTP), cytidine triphosphate (CTP), timidine triphosphate (TTP), and uridine triphosphate (UTP). These terms mean that the nucleotides contain ribose sugar.
Nucleotides containing deoxyribose sugar have the prefix deoxy- in name and d- in abbreviation: deoxyadenosine triphosphate (dATP), deoxyguanosine triphosphate (dGTP), deoxycytidine triphosphate (dCTP), deoxythymidine triphosphate (dTTP) U and deoxy urate.
One of the methods for obtaining the required gene (DNA molecule), which will be subject to replication (cloning) with the release of a significant number of replicas, is to construct a complementary DNA (cDNA) on mRNA. This method requires the use of reverse transcriptase, an enzyme that is present in some RNA-containing viruses and provides DNA synthesis on an RNA matrix.
The method is widely used to produce cDNA and involves the isolation of mRNA from total tissue mRNA, which encodes the translation of a specific protein (for example, interferon, insulin) with further synthesis on this mRNA as a matrix of the required cDNA using reverse transcriptase.
The gene that was obtained using the above procedure (cDNA) must be introduced into the bacterial cell so that it integrates into its genome. To do this, recombinant DNA is formed, which consists of cDNA and a special DNA molecule that rules as a conductor, or a vector capable of penetrating the recipient into the cell. Viruses or plasmids are used as vectors for cDNA. Plasmids are small circular DNA molecules that are separate from the nucleoid of a bacterial cell, contain several important genes for the function of the whole cell (for example, antibiotic resistance genes and can replicate independently of the main genome (DNA) of the cell. Biologically important and practically Plasmid properties that are useful for genetic engineering are their ability to move from one cell to another by the mechanism of transformation or conjugation, as well as the ability to be incorporated into the bacterial chromosome and replicate with her.