Read the paragraph given below and answer the question.
If a person is born with a hereditary disease, can a corrective therapy be taken for such a disease? Gene therapy is an attempt to do this. Gene therapy is a collection of methods that allows correction of a gene defect that has been diagnosed in a child/embryo. Here genes are inserted into a person's cells and tissues to treat disease.
ADA deficiency is caused due to:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Deletion of gene for adenosine deaminase
Option (1) Deficiency of bone marrow — Incorrect. The disorder is not a lack of bone marrow; bone marrow transplantation is one of its treatments.
Option (2) Deletion of gene for adenosine deaminase — Correct. ADA deficiency is caused by the deletion of the gene for adenosine deaminase. Without the gene the enzyme is not made, and the immune system cannot work.
Option (3) Addition of Adenosine — Incorrect. Nothing is added to the genome in this disorder. NCERT says ADA deficiency is caused by the deletion of the gene for adenosine deaminase.
Option (4) Deletion of amino group in genome — Incorrect. The cause is the deletion of a gene, not of an amino group.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
Gene Therapy – “… The first clinical gene therapy was given in 1990 to a 4-year old girl with adenosine deaminase (ADA) deficiency. This enzyme is crucial for the immune system to function. The disorder is caused due to the deletion of the gene for adenosine deaminase. In some children ADA deficiency can be cured by bone marrow transplantation; in others it can be treated by enzyme replacement therapy, in which functional ADA is given to the patient by injection.”