Treatment of ADA deficiency. 1. Gene therapy was used to correct the genetic disorder called Severe Combined Immuno Deficiency (SCID) syndrome produced by adenosine deaminase (ADA) deficiency.

2. In this, Normal ADA gene copies were produced by cloning.

3. Packed into defective retrovirus, most of the viral genes were replaced by ADA gene.

4. Lymphocytes were isolated from the patients.

5. Recombinant DNA of the recombinant retroviruses were used to infect the lymphocytes.

6. The infected cells expressing the ADA gene were injected back into the patients.

7. The normal ADA gene was then expressed in the patients and ADA deficiency is partially corrected. If the gene isolated from bonemarrous cells producing ADO is introduced into embryonic cells at early stages, it could provides permanent cure.

Steps involved in gene transfer for the production of growth hormone