Gene therapy is the method of correcting the defective gene responsible for producing a particular disease. This is accomplished by cutting out the defective gene with a restriction enzyme and inserting the corrected gene in its place.
This is done in two ways, namely:
(i) cells containing the corrected gene are grown in the laboratory and injected into the patient, or
(ii) a vector, usually a virus, is modified to carry human DNA with the corrected gene and injected directly into human target cells. The corrected DNA then binds to the target cell and cures the disease.
A virus can enter a cell and attach its DNA to the infected cell's chromosomes based on the following:
(i) Viruses can introduce drugs into target cells.
(ii) desired genes are introduced
(iii) can be widely applied in genetic engineering.
(vi) Hepatitis B virus antigen-producing gene is introduced into tobacco plants through TMV.
A hepatitis-B vaccine has been adopted. Tobacco no longer needs to be refrigerated like conventional vaccines. In rural areas, it can be consumed directly as a vaccine. It has not been released on the market yet.
(vii) Production of the oral vaccine in maize. It has also not been released to the market.
Molecular farming by developing transgenic animals using them as bio-reactors and all the necessary medicines are extracted from milk, blood, and excreta obtained from such animals.