10.2 Gene Therapy · Part 2

subsequently returned to the patient. Since these cells are not immortal, the patient requires periodic infusion of such genetically engineered lymphocytes. The disease could be cured permanently if the gene for ADA isolated from bone marrow cells are introduced into the cells of the early embryonic stages. XII Std Zoology Chapter XII Std Zoology Chapter Applications of Biotechnology differentiate into all types of cells that are derived from any of the three germ layers ectoderm, endoderm and mesoderm. In mammals there are two main types of stem cells – Embryonic Stem Cells (ES Cells) and adult stem cells. ES Cells are both pluripotent (can produce the three primary germ layers ectoderm, mesoderm and endoderm) and multipotent (can differentiate into a number of types of cells) (Fig. . ) . ES cells are isolated from the epiblast tissue of the inner cell mass of a blastocyst. When stimulated, ES Cells can develop into more than cells types of the adult body. ES Cells are immortal i.e., they can proliferate in a sterile culture medium and maintain their undifferentiated state. Adult stem cells are found in various tissues of children as well as adults. An adult stem cell or somatic stem cell can divide and create another cell similar to it. Most of the adult stem cells are involves the introduction of DNA into germ cells which is passed on to the successive generations. Gene therapy involves isolation of a specific gene and making its copies and inserting them into target cells to make the desired proteins. It is absolutely essential for gene therapists to ensure that the gene is harmless to the patient and it is appropriately expressed and that the body’s immune system does not react to the foreign proteins produced by the new genes.