logo
Products
Technologies
Applications
Services
Resources
Selection Guides
About
What is the difference between melting temperature and annealing temperature?
Posted June 22, 2020

Answer

The melting temperature (Tm) is the temperature at which 50% of the double-stranded DNA is changed to single-stranded DNA. It relies directly on the length and composition of the DNA molecule. A longer strand and a higher guanine-cytosine (GC) content are favorable for a higher melting temperature.

The annealing temperature is the temperature used in the annealing step of a PCR reaction, which is highly dependent on the Tm of primers. The annealing temperature should be low enough to allow both forward and reverse primers to bind to the single-stranded DNA, but not so low as to enable the formation of undesired, non-specific duplexes or intramolecular hairpins. Thereby, the annealing temperature is usually set as a few degrees (3-6) lower than the lowest Tm of the primers.