DNA can denature, or unwind, when the hydrogen bonds between its base pairs break. This typically occurs at temperatures between 90 °C and 99 °C. Which of the following DNA strands would be expected to denature at a higher temperature?
Strand 1:
5' TAAAGCTTACGATAA 3'
3' ATTTCGAATGCTATT 5'
Strand 2:
5' GCGTCCGGCGTAGCC 3'
3' CGCAGGCCGCATCGG 5'

• A. Strand 1 would denature at a higher temperature because A-T bonds are stronger than G-C bonds.
• B. Strand 2 would denature at a higher temperature because it has more G-C pairs, which form stronger bonds than A-T pairs.
• C. Strand 1 would denature at a higher temperature because it has fewer G-C pairs, allowing it to remain stable at high temperatures.
• D. Strand 2 would denature at a lower temperature because having more G-C pairs makes it more likely to break down earlier under heat.

Answer: (B)