On which of the following $\mathrm{DNA}$ strands will $\mathrm{UV}$ light have the most effect?

• A. A strand with a high concentration of $\mathrm{cytosine}$ bases
• B. A strand with a high concentration of $\mathrm{adenine}$ bases
• C. A strand with a high concentration of $\mathrm{guanine}$ bases
• D. A strand with a high concentration of $\mathrm{thymine}$ bases

Answer: (D)

Verified step by step guidance

1. Understand the effect of UV light on DNA: UV light can cause damage to DNA by inducing the formation of pyrimidine dimers, primarily affecting thymine and cytosine bases.
2. Identify the bases susceptible to UV-induced damage: Thymine and cytosine are pyrimidine bases, and UV light can cause them to form dimers, disrupting the DNA structure.
3. Consider the types of bases in the given options: Adenine and guanine are purine bases, which are less susceptible to UV-induced dimer formation compared to pyrimidine bases.
4. Evaluate the strand with the highest concentration of thymine bases: Since thymine is a pyrimidine base, a strand with a high concentration of thymine bases will be more affected by UV light due to the potential for dimer formation.
5. Conclude that the strand with a high concentration of thymine bases will have the most effect from UV light exposure, as thymine dimers are a common form of UV-induced DNA damage.