1. A new system of medicine gene therapy, may develop to treat some hereditary disease such as SCID, haemophilia etc.
2. It is the technique for curing genetic disease through replacing a “Faculty Gene” by a normal healthy functional gene.
3. The first gene therapy used in severe combined immune deficiency (SCID) Pateint.
4. Infact with SCID disorder lack the enzyme adenosine deaminase (ADA)
5. ADA enzyme involved in purine metabolism.
6. These patients have no functioning T & B lymphocytes.
7. The affected child of SCID develops recurrent infection early in life because they have no immune response against invading pathogen.
8. The ideal approach would be to give the patient a functioning ADA by gene therapy.
9. Thus, genetic disorder can be over come by introducing specific gene.

 Transfer of desired genes from one organism into another is an important aspect of genetic engineering.
 Gene transfer is achieved by two kinds of transfer methods:
(i) Indirect method through vectors or carriers and
(ii) Direct or vector less transfer method
 Vectorless Gene Transfer : Foreign genes can also be transferred directly by the following methods:
(a) Electroporation : It creates transients ( temporary pores) in the plasma membrane to facilitate entry of foreign DNA.
(b) Chemical mediated genetic transformation: It involves certain chemicals such as polyethylene glycol (PEG), that help in the uptake of foreign DNA into host cells.
(c) Microinjection : It is the introduction of foreign genes into plant or animal cells using microinjection or glass needles.
(d) Particle gun/ Biolistic method: It is a technique in which tungsten or gold particle coated with foreign DNA are bombarded into target cells to facilitate entry of the foreign genes.

(e) Liposome mediated gene transfer : In this method DNA encloses within lipid begs. These lipid begs fused with protoplast.