Which of the following is NOT an application of PCR ?

The correct answer is Option (4)-To cure ADA (adenosine diaminase) deficiency

Polymerase Chain Reaction (PCR) is a laboratory technique used to amplify and analyze DNA sequences. It is commonly used for applications such as paternity testing, detection of mutations in genes (including suspected cancer patients), and identifying genetic disorders. PCR is now routinely used to detect HIV in suspected AIDS patients. It is being used to detect mutations in genes in suspected cancer patients too. It is a powerful techqnique to identify many other genetic disorders. However, PCR itself is not a cure for genetic disorders like ADA deficiency. The cure for ADA deficiency involves gene therapy or enzyme replacement therapy rather than PCR.

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 a disease. Correction of a genetic defect involves delivery of a normal gene into the individual or embryo to take over the function of and compensate for the non-functional gene.
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.