Nucleic acid absorbs light at wavelength of 260 mm due to
## **Core Concept**
Nucleic acids, including DNA and RNA, have a specific characteristic that allows them to absorb ultraviolet (UV) light maximally at a wavelength of 260 nanometers (nm). This property is crucial for various laboratory techniques, including spectroscopy to quantify nucleic acid concentrations.
## **Why the Correct Answer is Right**
The correct answer, , is right because nucleic acids absorb light at 260 nm primarily due to the presence of **aromatic rings** in their nucleotide bases. The bases - adenine, guanine, cytosine, and thymine (or uracil in RNA) - have conjugated double bonds that allow them to absorb UV light maximally at 260 nm. This absorption is a result of the **π → π* transitions** within these aromatic rings.
## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not accurately represent the reason for nucleic acid absorption at 260 nm. Without the specific chemical structure or relation to nucleic acids, it's hard to directly refute, but it's not the correct association.
- **Option B:** This option is incorrect for similar reasons as Option A; it lacks direct relevance to the known biochemical reason for UV absorption by nucleic acids.
- **Option D:** This option is incorrect because, like Options A and B, it does not correctly relate to the biochemical basis of nucleic acid absorption of UV light at 260 nm.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the ability of nucleic acids to absorb light at 260 nm is the basis for **spectrophotometric quantification** of DNA and RNA. This is a common laboratory technique where the concentration of nucleic acids in a solution can be estimated by measuring the absorbance at 260 nm, using the fact that an absorbance of 1.0 at 260 nm corresponds approximately to 50 μg/mL of double-stranded DNA.
## **Correct Answer:** .