DNA Structure and Replication

ID #2063

Could you please describe melting temperature.

Let's say you have an aqueous solution of 1000 identical copies of a double stranded DNA molecule that's 5000 base pairs in length. The melting temperature is a calculation of the amount of heat that would be needed to get all 1000 of those molecules halfway denatured. In other words, on average, about 2,500 of the base pairs in a given molecule will have broken their hydrogen bonds, and the other 2,500 will still have their hydrogen bonding maintained. Since there are still plenty of H-bonds holding the strands together, the molecule as a whole will look like it's "bubbling" apart. Presumably the A-T base pairs are more likely to be the ones broken, but this also depends on what base pairs are in the immediate "neighborhood." What the melting temperature does not mean is the temperature needed to get 500 of those molecules fully denatured and the other 500 fully double stranded.

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