Biotechnological Applications In Medicine

The polymerase chain reaction (PCR) is used for the early detection of HIV in suspected AIDS patients because it can amplify even minute quantities of the viral nucleic acid to detectable levels, as explained in NCERT Class 12, Chapter 11 (Biotechnology and its Applications). Conventional methods relying on antibodies or symptoms detect infection only after the pathogen has multiplied considerably, whereas PCR identifies the genetic material long before clinical symptoms appear. This makes PCR an extremely sensitive molecular diagnostic tool. Gel electrophoresis is used to separate and visualise DNA fragments by size but cannot by itself amplify trace amounts of viral DNA from a patient sample. Gram staining is a bacterial classification technique and is irrelevant to a virus like HIV. Paper chromatography separates small molecules such as pigments and has no diagnostic role for viral nucleic acids. Because PCR works on the genetic material itself rather than on the body's delayed antibody response, it shortens the diagnostic window and supports timely intervention. A plausibility check confirms PCR: detecting a very low concentration of pathogen before symptom onset requires amplification of its nucleic acid, which only PCR among the listed options can perform.