In which aspect of DNA structure are hydrogen bonds most important?

• A. Forming the phosphodiester backbone
• B. Attaching phosphate groups to deoxyribose sugars
• C. Stabilizing the base pairing between complementary strands
• D. Determining the helical twist of the sugar-phosphate backbone

Answer: (C)

Verified step by step guidance

1. Understand the components of DNA structure: DNA consists of a sugar-phosphate backbone and nitrogenous bases that pair between two strands.
2. Recall that the phosphodiester backbone is formed by covalent bonds between the phosphate group of one nucleotide and the sugar of the next nucleotide, not hydrogen bonds.
3. Recognize that phosphate groups are covalently attached to deoxyribose sugars, which also involves covalent bonds rather than hydrogen bonds.
4. Focus on the role of hydrogen bonds: they occur specifically between complementary nitrogenous bases (adenine-thymine and guanine-cytosine) on opposite strands, stabilizing the double helix.
5. Conclude that hydrogen bonds are most important for stabilizing base pairing between complementary strands, rather than for the backbone structure or helical twist.