Content area
Full Text
Abstract: The nucleic acid hybridization is the process wherein two DNA or RNA single chains (mono-stranded) from different biological sources, make the double catenary configuration, based on contingent sequence homology of the two sources, resulting DNA-DNA, RNA-RNA or DNA-RNA hybrids. The purpose is identification or localization of certain nucleic acid sequences (genes) in the genome of some species. The target molecule representing the DNA, RNA or protein sequence that should be identified or located and the probe molecule who identify the target, by hybridization. Hybridization on a solid carrier is: Southern blotting, Northern blotting, Western blotting. Hybridization stages is: probe synthesis, probe marking (radioactively or non-radioactively), target DNA processing, target DNA denaturation, target DNA transfer to solid carrier, molecular hybridization.
Keywords: blotting, target, probe, primers, renaturation, vectors.
Introduction
Biosphere should be considered a commodity borrowed from the next generations, that should be returned in best conditions. Regardless the attitude of some groups of political and economic interests, that control the uninformed people, it is clear it will be impossible to feed the next generations (according to demographic forecasts, the next generations will be increasingly frequent) only with resources ensured by conventional technologies. Under the global circumstances, the genetic engineering techniques and especially the recombined DNA technology, gains more and more ground within modern technologies (Vassu et al, 2002). Identification, isolation and sequentialisation more easily and accurately of genes that codify various characters showing economic interest, is currently carried out by molecular hybridization techniques as well as in vitro and in vivo molecular cloning techniques (Chen et al., 1998, Yeung et al., 2002).
Results achieved by applying the hybridization methods are expressed in homology percentage. A reassociation percent higher than 70-80% proves conspecificity. It has been set that organisms within species should have at least 70% DNA homology by hybridization and at most 5% sequence divergence. This is the definition of "genomic" species in case of prokaryota (Stackebrandt and Goebel, 1994, Rossello-Mora and Amann, 2001). The studies of DNA hybridization have changed several times the conventional bacterial systematics, but it is compulsory to be joined by another technique, in order to be confirmed. For measurements, test strains from the surveyed taxon are recommended to be used, otherwise interpretation errors might occur (Vassu et al., 2002,...