In a melting profile for DNA, the absorbance at 260 nm increases as result of the disruption of the DNA structure. What is the fundamental physical basis for the absorbance increase?
A) the effective concentration of DNA changes
B) denatured DNA absorbs light more strongly than native DNA because the bases have become unstacked
C) native DNA absorbs light more strongly than denatured DNA because the bases are stacked
D) the absorbance of DNA is highly sensitive to temperature

Question

Quizplus · Accepted Answer

Denatured DNA absorbs light more strongly than native DNA because the bases, which were previously stacked and somewhat protected in the double helix structure, become unstacked and more exposed upon denaturation. This increased exposure allows the bases to absorb more UV light at 260 nm, leading to the observed increase in absorbance in the melting profile.

In a Melting Profile for DNA, the Absorbance at 260