Which one of the following techniques does not serve the purpose of...

Diagnosis of a disease at an early stage gives better opportunity to cure the same. Urine and serum analysis are a conventional way of diagnosis which can detect a disease only on the onset of the disease.

Recombinant DNA technology, Polymerase Chain Reaction (PCR) and Enzyme Linked Immuno-sorbent Assay (ELISA) are some of the techniques that serve the purpose of early diagnosis.

PCR is now routinely used to detect HIV in suspected AIDS patients. ELISA is based on the principle of antigen-antibody interaction. A single stranded DNA or even an RNA, tagged with a probe is allowed to hybridise to its complementary DNA in a clone of cells followed by detection using autoradiography. This is also used in detection of diseases.