Final answer:
As DNA unwinds and denatures, absorbance increases due to a phenomenon known as hyperchromicity, which occurs because more free nucleotides are available to absorb light.
Step-by-step explanation:
As DNA unwinds and denatures, the light absorbance at a wavelength of 260 nm typically increases. This is due to a phenomenon known as hyperchromicity.
When DNA is in its natural, double-stranded state, the base pairs are close together and block each other's ability to absorb light.
When the DNA unwinds and denatures, breaking the base pairs apart, more light is absorbed because there are more free nucleotides available to absorb the light, therefore resulting in an increased absorbance.
Learn more about DNA Unwinding