Which structural feature is crucial for the stability of the DNA double helix?

The stability of the DNA double helix heavily relies on hydrogen bonding between base pairs. Each base pair consists of specific nucleotides that form two or three hydrogen bonds with each other—adenine pairs with thymine through two hydrogen bonds, while guanine pairs with cytosine through three. These hydrogen bonds, although individually weak, collectively provide significant stability to the double helix structure when many base pairs are present along the length of the DNA molecule.

In addition, the orientation and arrangement of the base pairs allow the double helix to maintain its shape and structural integrity. This feature is vital for the functions of DNA, including replication and transcription, as it ensures that the sequence of nucleotides is preserved and accessible. While covalent bonds within the backbone contribute to the overall integrity of the DNA strand, it is the hydrogen bonding between the base pairs that plays a central role in the specific pairing and the helical structure's stability. Length of the DNA strands or protein interactions, while important in other contexts, do not directly determine the stability of the double helix in the same way as the hydrogen bonds do.