What type of bond holds the two strands of DNA together?

The two strands of DNA are held together primarily by hydrogen bonds. These bonds form between the nitrogenous bases on opposite strands of the DNA, specifically between adenine and thymine (A-T) with two hydrogen bonds, and between cytosine and guanine (C-G) with three hydrogen bonds. This specific pairing and bonding are essential for the double-helix structure of DNA, allowing the strands to stay together while also being able to separate during processes such as DNA replication and transcription.

The presence of hydrogen bonds offers sufficient strength to stabilize the DNA structure while allowing for the flexibility needed for these cellular processes. The other types of bonds mentioned, such as covalent bonds, play a different role in DNA structure. For instance, covalent bonds connect the sugar and phosphate backbone of each DNA strand, ensuring the integrity of the individual strand. Ionic bonds and peptide bonds are not involved in the base pairing of DNA strands, making hydrogen bonds the correct choice for holding the two strands together.