Practice question

Different viral strains show minimal morphological difference yet distinct genomic sequences. Polymerase chain reaction amplifies target nucleic acids using strain-specific primers, followed by sequencing or probe hybridization to identify mutations, genotypes, and lineages with high sensitivity. Fluorescence and electron microscopy reveal localization or ultrastructure but cannot resolve nucleotide variations. Clinical symptoms overlap among strains and are influenced by host immunity. Therefore, sequence-based amplification provides definitive, rapid, and sensitive discrimination, widely applied for influenza, SARS-CoV-2, and other viruses even at very low viral titers.