What type of bonds hold the nitrogenous bases together across the two DNA strands?

What type of bonds hold the nitrogenous bases together across the two DNA strands?

• A. Hydrogen bonds
• B. Covalent bonds
• C. Ionic bonds
• D. Peptide bonds

Answer: (A)

Hydrogen bonds hold the nitrogenous bases across the two DNA strands. A pairs with T through two hydrogen bonds, and G pairs with C through three hydrogen bonds, providing specific and relatively weak but sufficient attraction between the strands. This weaker bonding enables the double helix to open during replication and transcription. In contrast, the backbone of each strand is formed by strong covalent bonds linking sugars and phosphates (phosphodiester bonds). Ionic bonds aren’t used for base pairing, and peptide bonds connect amino acids in proteins, not DNA bases.

Hydrogen bonds hold the nitrogenous bases across the two DNA strands. A pairs with T through two hydrogen bonds, and G pairs with C through three hydrogen bonds, providing specific and relatively weak but sufficient attraction between the strands. This weaker bonding enables the double helix to open during replication and transcription. In contrast, the backbone of each strand is formed by strong covalent bonds linking sugars and phosphates (phosphodiester bonds). Ionic bonds aren’t used for base pairing, and peptide bonds connect amino acids in proteins, not DNA bases.