Biotechnological Applications In Medicine

Molecular diagnosis can detect a mutated gene using a labelled single-stranded DNA or RNA probe that pairs with its complementary sequence on the patient's nucleic acid, a process called hybridisation, as described in NCERT Class 12, Chapter 11 (Biotechnology and its Applications). The probe is tagged with a radioactive or fluorescent marker so that its binding to the target sequence can be detected; the presence or absence of a complementary site reveals whether a particular gene or mutation is present. Translation is the synthesis of proteins from messenger RNA and is a step of gene expression, not a diagnostic pairing technique. Transcription is the copying of DNA into RNA and likewise describes gene expression rather than probe-based detection. Conjugation is a mode of genetic transfer between bacteria and is unrelated to identifying mutations with a probe. Hybridisation is powerful in diagnosis because it can pinpoint a disease-causing allele even when it differs from the normal gene by only a small change, making it useful for detecting inherited disorders before symptoms appear. A consistency check confirms the answer: the diagnostic relies on complementary base pairing between a probe and target strand, which is exactly what molecular hybridisation means.