1
Question
How many of the following statements are true?
I. An ADA deficient patient requires infusion of genetically engineered lymphocytes periodically.
II. There is no need for periodic infusion if the ADA gene is introduced at the early embryonic stage.
III. ADA gene is introduced into lymphocytes by using Ti plasmid.
IV. Gene therapy using retroviral vectors may cause cancers in some patients.
V. Bone marrow transplantation and enzyme replacement therapy are completely curative.
How many of the following statements are true?
I. An ADA deficient patient requires infusion of genetically engineered lymphocytes periodically.
II. There is no need for periodic infusion if the ADA gene is introduced at the early embryonic stage.
III. ADA gene is introduced into lymphocytes by using Ti plasmid.
IV. Gene therapy using retroviral vectors may cause cancers in some patients.
V. Bone marrow transplantation and enzyme replacement therapy are completely curative.
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Solution
The correct option is C Three
Adenosine deaminase (ADA) enzyme is important for functioning of lymphocytes. Its deficiency can lead to Severe Combined Immunodeficiency (SCID). It is a life threatening condition as there is no proliferation of lymphocytes. Such children are prone to opportunistic infections leading to death. In some children ADA deficiency can be partially cured by bone marrow transplantation from a matched donor. Besides, 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 is that they are not completely curative.
Gene therapy is another approach for ADA deficiency treatment where lymphocytes from the blood of the patient are grown in a culture outside the body. A functional ADA cDNA (complementary DNA synthesised from mRNA) is then introduced into these lymphocytes using disarmed/ harmless retroviral vectors. These lymphocytes are subsequently returned to the patient. As these cells are not immortal, the patient requires periodic infusion of such genetically engineered lymphocytes. If the ADA gene isolated from marrow cells is introduced into the cells at early embryonic stages, it could be a permanent cure. When gene therapy is performed in the stem cells of the embryonic stage, only the corrected cells are propagated which makes it a permanent cure.
Ti plasmid, obtained from Agrobacterium tumefaciens, is used for gene transfer in plants only, as it is a natural vector of dicotyledonous plants.
Adenosine deaminase (ADA) enzyme is important for functioning of lymphocytes. Its deficiency can lead to Severe Combined Immunodeficiency (SCID). It is a life threatening condition as there is no proliferation of lymphocytes. Such children are prone to opportunistic infections leading to death. In some children ADA deficiency can be partially cured by bone marrow transplantation from a matched donor. Besides, 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 is that they are not completely curative.
Gene therapy is another approach for ADA deficiency treatment where lymphocytes from the blood of the patient are grown in a culture outside the body. A functional ADA cDNA (complementary DNA synthesised from mRNA) is then introduced into these lymphocytes using disarmed/ harmless retroviral vectors. These lymphocytes are subsequently returned to the patient. As these cells are not immortal, the patient requires periodic infusion of such genetically engineered lymphocytes. If the ADA gene isolated from marrow cells is introduced into the cells at early embryonic stages, it could be a permanent cure. When gene therapy is performed in the stem cells of the embryonic stage, only the corrected cells are propagated which makes it a permanent cure.
Ti plasmid, obtained from Agrobacterium tumefaciens, is used for gene transfer in plants only, as it is a natural vector of dicotyledonous plants.
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