Q.Explain three practical applications of PCR for early diagnosis and treatment of diseases. OR Explain three therapeutic engineered products along with their use.

Part (i): PCR enables very early, sensitive diagnosis (HIV, cancer mutations, infectious pathogens) by amplifying trace DNA. Part (ii): genetically engineered therapeutic products include insulin (Humulin), gene therapy for ADA deficiency, and a recombinant hepatitis B vaccine.

Part (i) — Three practical PCR applications for early diagnosis:

1. Early detection of HIV: PCR can detect the HIV viral genome directly in blood very early in infection, even before antibody levels are high enough for conventional antibody-based tests to detect — enabling much earlier diagnosis.
2. Detection of cancer-related mutations: PCR can amplify and help identify mutations in specific genes (oncogenes) in patients suspected of a genetic predisposition to cancer, supporting early diagnosis and monitoring.
3. Detection of infectious pathogens: PCR can amplify and detect pathogen DNA (e.g. Mycobacterium tuberculosis in suspected TB) from very small clinical samples, allowing faster, more sensitive diagnosis than traditional culture methods, so treatment can start earlier.

Part (ii) — OR: Three therapeutic engineered products and their use:

1. Insulin (Humulin): the human insulin gene (A and B chains) was cloned and expressed in genetically engineered E. coli, producing human insulin commercially — used to treat diabetes mellitus, replacing insulin earlier extracted from animal pancreas.
2. Gene therapy for Adenosine Deaminase (ADA) deficiency: in this inherited immune disorder (a form of SCID), a functional ADA gene is introduced into the patient's lymphocytes (via a retroviral vector) to correct the enzyme deficiency and restore immune function. …