DNA probes and sample DNAs or RNAs are capable of hybridizing each other through the complementary base-pairing and result in double-stranded hybrid formation. The strength of DNA probe hybridization to sample molecules is determined by the stability of the hybrid duplex formed. The other parts of each sample molecule, which is usually longer than DNA probe, remains on either side of the hybrid duplex and does not affect the hybridization strength since they have no interactions with the probe. The formed hybrid duplexes may be melted into single-stranded random coils by elevating temperature. Their thermal stability under a given solvent condition is determined by three factors: (i) the G+C content and base sequence of DNA probes, (ii) the length of hybrid duplexes, and (iii) base mismatches in hybrid duplexes. The last factor allows the detection of base sequence difference between DNA probes and sample DNAs or RNAs using the thermal stability of the hybrid duplex, and thus provides the basis of DNA probing. You can share your ideas & comments further at : molecularbiology@scholarlymed.com molecularbiology@scholarlymed.com