Human beings suffer from more than 5000 different disease caused by single gene mutations, e.g., cystic fibrosis, acatalasia, Huntington's chorea, Tay sach's disease, Lesch- Nyhan syndrome, sickle cell anemia, mitral stenosis, Hunter's syndrome, haemophilia, several forms of muscular dystrophy etc. in addition, many common disorders like cancer, hypertension, atherosclerosis, and mental illness seem to have genetic components. Malignant cells may arise due to mutations in two types of genes,viz oncogenes and tumor suppressor genes.
Gene therapy may be defined in broad general terms as follows: introduction of a normal functional gene into cells, which contain the defective allele of concerned gene with the objective of correcting a gene disorder or an acquired disorder. The meaning of gene therapy has now been made much broader to include attempts to cure any disease by the introduction of a cloned gene into the patients. application of gene therapy involves the following basic development in genetics molecular biology & biotechnology:
1. Identification of the gene that plays the key role in the development of the genetic disorder,
2. Determination of the ole of its product in health & disease,
3. Isolation & cloning of the gene
4. Development of an approach to gene therapy
TYPES OF GENE THERAPY
Gene therapy may classified in to the following types:
Germ line gene therapy
Somatic cell gene therapy
In case of germ line gene therapy, germ cells, i.e., sperms or eggs, are modified by the introduction f functional genes, which are ordinarily integrated into their genomes. Therefore, the change due to therapy would be heritable and would be passed on to later generations. This approach, theoretically, should be highly effective in counteracting the genetic disorders. However, this option is prohibited, at least for the present, for application in human beings for a variety of technical & ethical reasons.
In somatic cell gene therapy, the gene is introduced only in somatic cells, especially of these tissues in which expression of the concerned gene is critical for health. Expression of the introduced gene relives/ eliminates symptoms of the disorder, but this effect is not heritable as it does not involve the germ line. somatic cell therapy is the only feasible option, & clinical trials have already been started mostly for the treatment of cancer and blood disorders.
Suitable Candidates for Gene Therapy:
1. Cystic fibrosis
3. Familial Hypercholesterolemia
5. Marfan syndrome
6. Huntingtons disease
7. Sickle cell anemia
8. Tay sachs disease
10. Colour Blindness