Gene Therapy
மரபணு சிகிச்சை
Stop confusing Gene Therapy with Recombinant DNA technology. Gene therapy is the clinical application, not just the tool. If you cannot distinguish between 'in vivo' and 'ex vivo' delivery, you are losing marks on a fundamental concept.
The idea
Gene therapy is a collection of methods used to correct a diagnosed genetic defect in a child or embryo. It involves delivering a normal, functional gene into the cells to compensate for the non-functional gene. This functional gene integrates into the genome to restore normal protein synthesis. It is the definitive approach to treating hereditary diseases at the molecular level.
Why it matters
It exists to provide a curative approach for genetic disorders that cannot be treated effectively by conventional medicine.
NEET lens
NEET focuses on the ADA deficiency case study. Memorize the year 1990 and the specific enzyme involved. Distinguish between permanent cure (bone marrow transplantation) and temporary gene therapy (periodic lymphocyte infusion). Expect questions on the mechanism of gene delivery into the patient's cells.
Clinical significance
The first clinical gene therapy was given in 1990 to a 4-year-old girl with Adenosine Deaminase (ADA) deficiency. ADA is critical for the immune system; its absence leads to Severe Combined Immunodeficiency (SCID). Without functional ADA, lymphocytes fail to mature, leaving the patient vulnerable to fatal infections.
Introduction
Gene therapy is a collection of methods that allows correction of a gene defect diagnosed in a child or embryo — genes are inserted into a person's cells and tissues to treat a disease.
Core concept
First clinical gene therapy (1990): given to a 4-year-old girl with adenosine deaminase (ADA) deficiency. ADA is crucial for the immune system to function; the disorder is caused by deletion of the gene for adenosine deaminase. Some children can be cured by bone marrow transplantation, others by enzyme replacement therapy (functional ADA given by injection), but both are not completely curative. In gene therapy, lymphocytes from the patient's blood are grown in culture outside the body; a functional ADA cDNA is introduced into these lymphocytes using a retroviral vector; the lymphocytes are returned to the patient. Since these cells are not immortal, the patient needs periodic infusion of such genetically engineered lymphocytes. If the gene isolated from marrow cells producing ADA is introduced into cells at early embryonic stages, it could be a permanent cure.
Go deeper
Gene therapy corrects the cause (the defective gene) instead of only treating symptoms; retroviruses are 'disarmed' to serve as the delivery vehicle.
From Class 10
Some diseases happen because one gene doesn't work. Gene therapy tries to give the patient a working copy of that gene.