Practice question

Among routine molecular techniques, PCR uniquely amplifies specific DNA sequences from minute starting material through exponential replication, achieving detectable quantities from single copies. ELISA detects proteins via antibody-antigen interactions without nucleic acid amplification. Northern blot and FISH involve hybridization for detection but lack exponential synthesis, requiring microgram amounts of RNA or DNA. Hence forensic samples, ancient DNA, viral loads, and biopsy specimens are analyzable only by PCR, including conventional, nested, and quantitative real-time variants that drastically enhance sensitivity and enable diagnostics and research.