Explain how a hereditary disease can be corrected. Give an example of first successful attempt made towards correction of such diseases.

Gene therapy can be used to correct hereditary diseases. It involves 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. In this disease, the gene coding for enzyme ADA gets deleted leading to deficiency of ADA and problems in immune system. Gene therapy for ADA deficiency includes isolation of lymphocytes from patient’s blood, culturing them in-vitro, introduction of functional ADA cDNA and returning the cells to the patient’s body.