What type of bond holds the DNA bases together?

The correct answer is hydrogen bonds, which play a crucial role in the structure of DNA. In the double helix structure of DNA, the bases from opposite strands pair with each other—adenine pairs with thymine, and cytosine pairs with guanine. The attraction between these base pairs is facilitated by hydrogen bonds.

Specifically, there are two hydrogen bonds forming between adenine and thymine, and three hydrogen bonds forming between cytosine and guanine. These hydrogen bonds are essential for maintaining the stability of the DNA structure while allowing the strands to separate easily during processes such as DNA replication and transcription.

Covalent bonds are indeed found in DNA as well, but they connect the sugar and phosphate backbone, rather than holding the bases together. Ionic bonds typically involve the attraction between charged particles and do not play a role in the structure of the DNA base pairing. Peptide bonds are relevant in the context of proteins, linking amino acids together, but are not involved in the bonding of DNA bases.