In fact, the melting temperature of the DNA molecule is the temperature at which exactly half of that double helix structure has essentially dissociated. Now, the next question is if we have a beaker and inside that beaker we have a solution of DNA molecules and we begin to increase the temperature, we begin to heat that solution. How can we measure in a laboratory how much of the DNA has actually dissociated? Well, one way we can measure the dissociation of our DNA is by measuring how much UV light, how much UV radiation is actually absorbed by the DNA molecule. Now, why is that important. Why is UV radiation or absorbents of UV radiation relevant?