Which type of bond is created between nitrogenous bases in DNA?

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

Answer: (D)

The bond formed between nitrogenous bases in DNA is a hydrogen bond. In the double helical structure of DNA, the nitrogenous bases pair specifically: adenine pairs with thymine, and cytosine pairs with guanine. Each of these pairs is held together by hydrogen bonds, which are relatively weak interactions compared to covalent bonds. This characteristic is crucial for the DNA structure, as it allows the two strands of the helix to separate during processes like replication and transcription.

Covalent bonds, on the other hand, are strong bonds that link the sugar and phosphate backbone of the DNA molecule, but they do not connect the bases. Peptide bonds are specific to proteins and involve the linking of amino acids, while ionic bonds involve the electrostatic attraction between charged particles, which is not a characteristic bond in the structure of DNA bases. Thus, the fundamental interactions between the nitrogenous bases are specifically hydrogen bonds, allowing for the stability and flexibility of the DNA structure.