Final answer:
Hydrogen bonds between the complementary nitrogen bases of nucleotides hold the two strands of a DNA molecule together, allowing for the double-helix structure. These bonds are weaker than the covalent bonds in the sugar-phosphate backbone, enabling the DNA to unzip for replication.
Step-by-step explanation:
The hydrogen bonds in DNA play a crucial role in the molecule's structure and function. Two strands of a DNA molecule are held together by hydrogen bonds that form between the complementary nitrogen bases of the nucleotides. In the iconic double-helix structure, the strands are oriented antiparallel to each other, with the bases facing inwards. Each base on one strand forms a hydrogen bond with a complementary base on the opposite strand: adenine (A) with thymine (T), and cytosine (C) with guanine (G). This pairing is facilitated by the sugar-phosphate backbone, which forms the exterior of the DNA double-helix.
The ability of DNA to “unzip” down the middle is made possible because the hydrogen bonds are relatively weak compared to the strong covalent bonds that hold together the individual atoms in the DNA backbone. This feature is critical for DNA replication as it allows each strand to serve as a template for creating a new complementary strand.
Overall, the cumulative effect of the millions of hydrogen bonds not only maintains the overall structure of the DNA double helix but also allows it to function efficiently in the replication process.