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Gene Therapy is advisable for genetic diseases which cannot be cured. Here stem cells are very important and most potent cells which can be used for gene therapy and after that they can be transplanted in to human. For gene therapy, DNA can be efficiently introduced with homologous recombination as for gene therapy we need to correct the specific gene defect without addition of harmful extraneous DNA sequences. Such correction is possible with homologous recombination between input DNA sequences and identical homologous sequences in the genome for target gene. To select the target cells, there are techniques for developing virtually pure populations of hematopoietic stem cells from heterogeneous population and it should permit the use of the highly efficient nuclear microinjection methods for transfer of DNA. It is important that the therapeutic DNA introduced into target cells must remain functional and the cells containing the therapeutic DNA must be long-lived and stable. Problems with integrating therapeutic DNA into the genome and the rapidly dividing nature of many cells prevent gene therapy from achieving any long-term benefits. Techniques combined with new highly sensitive methods for detecting cells with the specified genetic modification of non-expressed genes would make homologous recombination-mediated gene therapy feasible for hematopoietic stem cells. Now stem cell based gene therapy has been introduced for many genetic diseases like Leukemia and recently for skin diseases.

Sometime obtaining the stem cells from same individual is difficult and to come up with this problem in future it was suggested to derive the stem cells from placental cord at the time of baby birth. In recent development, obtaining stem cells from placental cord and cryo-preservation of them for future use has been introduced. This can be used once someone will be identified with genetic disorder. It is expected that the development in recent studied of stem cell based gene therapy will be revolutionary in future of health science.