Which of the following statements is/are incorrect about Gene therapy? 1. It is a collection of methods that allows correction of a gene defect that has been diagnosed in a child/embryo. 2. ADA deficiency cannot be cured by bone marrow transplantation.
Gene therapy is a collection of methods that allows correction of a gene defect that has been diagnosed in a child/embryo . Hence, Statement1 is correct. Here genes are inserted into a person’s cells and tissues to treat a disease. Correction of a genetic defect involves the delivery of a normal gene into the individual or embryo to take over the function of and compensate for the non-functional gene. The first clinical gene therapy was given in 1990 to a 4-year old girl with adenosine deaminase (ADA) deficiency. This enzyme is crucial for the immune system to function . The disorder is caused due to the deletion of the gene for adenosine deaminase . In some children, ADA deficiency can be cured by bone marrow transplantation. Hence, Statement 2 is not correct. in others, it can be treated by enzyme replacement therapy , in which functional ADA is given to the patient by injection. But the problem with both of these approaches that they are not completely curative . As a first step towards gene therapy, lymphocytes from the blood of the patient are grown in a culture outside the body . A functional ADA cDNA (using a retroviral vector ) is then introduced into these lymphocytes , which are subsequently returned to the patient. However, as these cells are not immortal, the patient requires a periodic infusion of such genetically engineered lymphocytes. However, if the gene isolate from marrow cells producing ADA is introduced into cells at early embryonic stages , it could be a permanent cure.