Which statement correctly compares covalent bonds and hydrogen bonds in DNA?

Which statement correctly compares covalent bonds and hydrogen bonds in DNA?

• A. Covalent bonds are weaker than hydrogen bonds.
• B. Hydrogen bonds are stronger than covalent bonds.
• C. Ionic bonds are stronger than covalent bonds.
• D. Covalent bonds are stronger than hydrogen bonds.

Answer: (D)

Bond strength differences between covalent bonds and hydrogen bonds are what's being tested here. Covalent bonds share electrons and form the sugar–phosphate backbone of DNA, making them very strong, typically hundreds of kilojoules per mole. Hydrogen bonds are weaker attractions between base pairs, guiding specific A–T and G–C pairing, and they can be broken and reformed much more readily. This difference in strength explains why the backbone stays intact while the two strands can unzip during replication or transcription. So, covalent bonds are stronger than hydrogen bonds in DNA. The other statements either reverse the relative strengths or bring in bonds (like ionic) that aren’t the main players in DNA’s double-helix stability.

Bond strength differences between covalent bonds and hydrogen bonds are what's being tested here. Covalent bonds share electrons and form the sugar–phosphate backbone of DNA, making them very strong, typically hundreds of kilojoules per mole. Hydrogen bonds are weaker attractions between base pairs, guiding specific A–T and G–C pairing, and they can be broken and reformed much more readily. This difference in strength explains why the backbone stays intact while the two strands can unzip during replication or transcription. So, covalent bonds are stronger than hydrogen bonds in DNA. The other statements either reverse the relative strengths or bring in bonds (like ionic) that aren’t the main players in DNA’s double-helix stability.