(a) Name the source of Taq polymerase. Explain the advantage of its use in biotechnology.
(b) Expand the name of the enzyme ADA. Why is the enzyme essential in the human body ? Suggest a gene therapy for its deficiency.
(a) Taq polymerase was originally isolated from the thermophilic bacterium - Thermus aquaticus. This enzyme is thermostable. DNA polymerase is used in the process of DNA replication normally but at high temperature it gets denatured. In PCR the mixture need to be heated above
90C to denature the newly formed DNA allowing the strands to separate and act as templates in the next round. The enzyme Taq polymerase is thermostable and eliminates the need for having to add new enzyme to PCR.
(b) 1. Enzyme is adenosine deaminase. It is needed for proper functioning of immune system.
2. Gene therapy is the technique of genetic engineering to replace a 'faulty gene' by a normal healthy functional gene. ADA deficiency is caused due to defect in the gene for the enzyme adenosine deaminase.
3. In some children ADA deficiency can be cured by bone marrow transplantation.
4. It can also be treated by enzyme replacement therapy in which functional ADA is given to the patient by injection.
5. As a first step towards gene therapy, lymphocytes, a kind of white blood cells, are extracted from the bone marrow of the patient and are grown in a culture outside the body. A functional ADA cDNA (using a retroviral vector) is then introduced into these lymphocytes which are reinjected into the patients's bone marrow.
6. But as these cells do not always remain alive, the patient requires periodic infusion of such genetically engineered lymphocytes. However, if the isolated gene from bone marrow cells producing ADA is introduced into cells at embryonic stages, it can be a permanent cure.