What type of bond holds two nitrogen bases together?

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

Answer: (A)

In DNA, two nitrogen bases are held together by hydrogen bonds. These are weak, non-covalent interactions formed when a hydrogen atom attached to a highly electronegative atom (such as nitrogen or oxygen) forms a bridge to another electronegative atom. Specifically, A pairs with T using two hydrogen bonds, and C pairs with G using three hydrogen bonds, providing both specificity and enough stability to keep the strands together while still allowing them to separate during replication and transcription. Covalent bonds lock the sugar-phosphate backbone of each strand, not the base pairs; ionic and metallic bonds aren’t the primary forces stabilizing base pairing.