Q.Explain with an example, how molecular diagnostic techniques are helpful in early diagnosis of the diseases.

Molecular diagnostic techniques like PCR and ELISA can detect a pathogen or a disease-linked gene mutation much earlier than traditional symptom-based diagnosis.

Conventional methods of disease diagnosis (based on the appearance of symptoms) usually become positive only after the pathogen has multiplied to a sufficiently high level in the body, by which point the disease has progressed considerably. Recombinant DNA technology-based molecular diagnostic techniques allow much earlier detection.

Example — PCR (Polymerase Chain Reaction): used to detect suspected pathogen DNA/RNA (e.g., HIV in AIDS patients, or the causative bacterium/virus of other infectious diseases) by amplifying a single/few copies of the pathogen's nucleic acid present in a patient's sample to millions of copies, so that the presence of the pathogen can be detected even at a very early stage of infection, well before the disease itself is detectable by conventional means. PCR is also used to detect mutant alleles in genetic disorders in suspected/prenatal cases, and to detect cancer-related gene mu …