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Genetic engineering is not without reason called a technology of the century. It is defined differently, hence the many controversies when discussing its usefulness and abuse of this technology. Genetic engineering is often presented as a possibility of in vitro gene manipulation, where the meaning of manipulation is not clear and may be associated with abuse. However, the acceptable definition describes it as a target change and recombination, as well as insertion and further propagation of recombinant rDNA in living cells. According to this definition, the basic Genetic engineering criteria include cutting DNA molecules, joining cut fragments with DNA fragments from the same or different sources, insertion of such recombinant molecules in the cell where, if needed, it will continue to multiply or express specifically.

Reverse Transcriptase and Restriction Endonucleases
The development of genetic engineering begins with the discovery of the enzyme called reverse transcriptase (RNA-dependent DNA polymerase) and a group of enzymes called restriction endonucleases. These enzymes cut foreign DNA in places with specific arrangement of nucleotides. So far, hundreds of different restriction endonucleases are isolated, that cut both tracks DNA at specific places. These enzymes were named according to the bacteria from which they were isolated. Thus EcoRI isolated from Escherichia coli, and restriction endonuclease Hindia from Haemophilus influenzae. DNA fragments cut by restriction endonucleases may have such ends that spontaneously tend to merge, and they are called "sticky" ends, or they can be without this property and then are called "Blind" ends.

Other Methods
Besides the restriction endonuclease, other methods are also used:
- Enzymes which allow reconnection of broken pieces of DNA (DNA ligase)
- Procedures for inserting rDNA into the cell where it would be replicated
- Methods for the selection of clones of cells containing rDNA

The Use of Plasmids
Insertion of DNA into the cell is effectively carried out using vectors (DNA molecules with the ability of Self-replication in a host cell). The most commonly used vectors are plasmids (extrachromosomal bacterial DNA with the ability self-reproduction), bacteriophages, DNA and RNA viruses and cosmids (artificially constructed vectors). The use of plasmids in the experiments has the advantage because of the possibility of relatively simple determining which cells are transformed with the recombinant plasmid. Plasmids are the most common gene carriers for resistance to antibiotics. Insertion of foreign DNA in a region of the gene for resistance to antibiotic is associated with the loss of resistance of bacteria to an antibiotic. Since the plasmids that are used contain the genes for resistance to other antibiotics, growing bacteria on nutrient media containing those antibiotics allows selection of clones with recombinant bacterial plasmid. One of the lack of plasmids is that they often can not be stable if they contain large DNA fragments , and therefore, for this purpose the viruses and cosmids are used.

Vaccine Production
Production of vaccines from the standpoint of our problems, it is very interesting, because any potential aggressor will try to protect their own units from the biological agents used. Production of the vaccine is a relatively simple process, and produced vaccines are nontoxic, avirulent and more efficient than existing vaccines.

Detection
The use of genetic engineering for diagnosis significantly improves the ability of detection of the used biological weapons. The techniques of genetic engineering require small sample, and the techniques are very sensitive and accurate.

Changing The Genetic Structure of Microorganisms
Using genetic engineering when changing the genetic structure of microorganisms is consisted in general of three established procedures:

a) Transformation (procedure in which parts of the DNA from other microbes are introduced into the cell of the agent examined by changing some properties of it.
Using this procedure we can change resistance and virulence of the organisms.

b) Transduction (the process of introduction of the new genes into the organism through certain bacterial viruses. This phenomenon occurs spontaneously in nature)

c) Conjugation is crossing of mutual similar microorganisms with mutual changes of biological properties. This method has rather unpredictable results.

Conclusion
Undoubtedly, genetic engineering can be abused for changing the microorganisms in order to make them more virulent, resistant to some antibiotics or most antibiotics, and it’s even possible to make such changes that cause the new microorganism not to resemble the initial strain any more. As in many other cases, large scientific discoveries are preceded by the military aimed studies. If the genetic engineering in civil laboratories is so advanced, the question is how advanced military labs are and in what direction? At a time when many countries are conducting research in the field of genetic engineering, and the results are not published for over twenty years, the danger is not to be underestimated.