What type of bond forms between nucleotides?

What type of bond forms between nucleotides?

• A. Covalent bonds (strong) form between nucleotides.
• B. Hydrogen bonds (weak) form between nucleotides.
• C. Ionic bonds form between nucleotides.
• D. Disulfide bonds form between nucleotides.

Answer: (A)

Nucleotides are linked to form the DNA backbone by covalent bonds called phosphodiester bonds. Each bond connects the 3' carbon of one sugar to the 5' phosphate of the next nucleotide, creating a strong, continuous sugar–phosphate chain. This covalent linkage is what gives DNA its structural stability in a single strand. Hydrogen bonds, on the other hand, occur between paired bases on opposite strands to hold the double helix together, and they are much weaker. Ionic bonds and disulfide bonds do not form the backbone connections between nucleotides—ionic interactions are charge-based and disulfide bonds occur between cysteine residues in proteins, not between nucleotides.

Nucleotides are linked to form the DNA backbone by covalent bonds called phosphodiester bonds. Each bond connects the 3' carbon of one sugar to the 5' phosphate of the next nucleotide, creating a strong, continuous sugar–phosphate chain. This covalent linkage is what gives DNA its structural stability in a single strand. Hydrogen bonds, on the other hand, occur between paired bases on opposite strands to hold the double helix together, and they are much weaker. Ionic bonds and disulfide bonds do not form the backbone connections between nucleotides—ionic interactions are charge-based and disulfide bonds occur between cysteine residues in proteins, not between nucleotides.