In a DNA double helix, what primarily holds the two strands together?

In a DNA double helix, the two strands are primarily held together by hydrogen bonds between the paired bases. Each base on one strand forms specific hydrogen bonds with a complementary base on the opposite strand; for instance, adenine pairs with thymine through two hydrogen bonds, while guanine pairs with cytosine through three hydrogen bonds. This base pairing is crucial for the stability and integrity of the DNA structure, allowing the two strands to remain associated while still enabling the strands to separate during processes such as DNA replication and transcription.

Covalent bonds play a different role in DNA. They are present between the phosphate and sugar groups of the backbone of each DNA strand, providing structural stability to the individual strands themselves but not holding the strands together. Ionic bonds between phosphate groups do not significantly contribute to the double helix structure, as the charges are neutralized by the surrounding environment, including the presence of cations in the cellular context.

Hydrophobic interactions can influence the DNA structure slightly, mainly by minimizing contact with water due to the nonpolar bases, but they are not the primary force maintaining the double helix. The hydrogen bonds are the key feature that enables the specific pairing necessary for the DNA’s functional properties, making this choice the most accurate in describing