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

The two strands of DNA are held together primarily by hydrogen bonds. These bonds form between the nitrogenous bases that are on opposite strands of the DNA double helix. Specifically, adenine pairs with thymine through two hydrogen bonds, while cytosine pairs with guanine through three hydrogen bonds. This pairing is essential for the stability of the DNA structure and allows for the precise duplication of genetic information during cellular processes such as replication.

The choice of hydrogen bonds is particularly significant because they are relatively weak compared to other types of bonds, such as covalent bonds, which are strong and hold the atoms within the individual nucleotide units together. The weakness of hydrogen bonds allows the DNA strands to separate easily during replication and gene expression, facilitating access to genetic information. Other bond types, such as ionic bonds and peptide bonds, do not play a role in maintaining the structure of DNA strands. Ionic bonds typically form between charged atoms, while peptide bonds link amino acids in proteins, not nucleic acids.