Question

A researcher heats a solution of DNA and notices that as the temperature increases, the absorbance of ultraviolet light at 260 nm increases dramatically. This is because __________.

Answer 1

The question is incomplete as it does not have the options which are:

1. there are more base pairs synthesized
2. the DNA becomes supercoiled
3. the double strands of DNA are separating
4. DNA gyrase relaxes supercoiling of the DNA

Answer:

3. the double strands of DNA are separating

Explanation:

Ultraviolet light is absorbed by the DNA molecule therefore the UV light is used to find the DNA concentration of a sample.

The ultraviolet light is absorbed by the nitrogenous bases present between the sugar-phosphate backbone of the DNA molecule. The part of the base which absorbs the UV light is the presence of the heterocyclic rings.

Since these heterocyclic rings are involved in the hydrogen bond therefore when DNA exists in its double-stranded form, it absorbs less UV light.

When the DNA sample is heated then the DNA gets denatured and DNA becomes single-stranded. The heterocyclic rings absorb the UV light more easily thus increasing the absorbance.

Thus, Option-3 is correct.