Gene Therapy-Definition, Types and ethical issues - MyTecNika

Breaking

Gene Therapy-Definition, Types and ethical issues

Gene Therapy

 What is gene therapy?

Gene therapy is a medical approach that treats or prevents disease by correcting the underlying genetic problem. Gene therapy techniques allow doctors to treat a disorder by altering a person’s genetic makeup instead of using drugs or surgery.

 introduction:

Human beings suffer from more than 5,000 different diseases caused by single gene mutations, e.g., cystic fibrosis, acatalasia, Huntington's chorea, Tay sach's disease, Lesch-Nyhan syndrome, sickle cell anaemia, mitral stenonsis, 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 tumour suppressor genes; both the types of mutant alleles are involved in malignant transformation of cells. 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 genetic 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 patient. 

Application of gene therapy involves the following basic developments in genetics, molecular biology and biotechnology: 

(i) identification of the gene that plays the key role in the development of a genetic disorder,

 (ii) determination of the role of its product in health and disease, 

(iii) isolation and cloning of the gene, and

 (iv) development of an approach for gene therapy.

The candidate disorders for gene therapy are selected on the basis of the following criteria:

(i) the disease should be life-threatening,

(ii) the gene responsible for the disease should have been cloned,

iii) a precise regulation of the gene should not be required, and

 (iv) a suitable delivery system should be available.

Types of Gene Therapy

Gene therapy may be classified into the following two types:

(i)   germ line gene therapy: In case of germ line gene therapy, germ cells, i.e., sperms or eggs (even zygotes), are modified by the introduction of 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 and ethical reasons.

ii) somatic cell gene therapy:  

In somatic cell gene therapy, the gene is introduced only in somatic cells, especially of those tissues in which expression of the concerned gene is critical for health. Expression of the introduced gene relieves/eliminates symptoms of the disorder, but this effect is not heritable as it does not involve the germline. Somatic cell therapy is the only feasible option, and clinical trials have already started mostly for the treatment of cancer and blood disorders. This approach is divided into the following two groups on the basis of the end-result of the process:

In somatic cell gene therapy, the gene is introduced only in somatic cells, especially of those tissues in which expression of the concerned gene is critical for health. Expression of the introduced gene relieves/eliminates symptoms of the disorder, but this effect is not heritable as it does not involve the germline. Somatic cell therapy is the only feasible option, and clinical trials have already started mostly for the treatment of cancer and blood disorders. This approach is divided into the following two groups on the basis of the end-result of the process:

(i)    addition or augmentation gene therapy

(ii) targetted gene transfer.