What type of bonds connect the nitrogenous bases in DNA?

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

Answer: (B)

Base pairing is held together by hydrogen bonds between the nitrogenous bases. These non-covalent bonds form specifically between complementary pairs: adenine pairs with thymine using two hydrogen bonds, and guanine pairs with cytosine using three hydrogen bonds. The weaker nature of hydrogen bonds makes the two DNA strands stable yet easily separable during replication and transcription, which is essential for copying genetic information. The backbone of DNA, by contrast, is connected by covalent phosphodiester bonds along each strand, not between the bases. Ionic or metallic bonds aren’t involved in base pairing.