Final answer:
Hydrogen bonds hold the nitrogen bases together in the DNA double helix, allowing for complementary base pairing of adenine with thymine, and cytosine with guanine, ensuring uniform spacing and structure of the DNA molecule.
Step-by-step explanation:
The hydrogen bonds hold the nitrogen bases together in the DNA twisted configuration, known as the double helix. The DNA molecule consists of two polynucleotide chains that are twisted around each other, with the sugar and phosphate forming the backbone of the nucleotide chains. Complementary base pairing occurs between specific nitrogenous bases; adenine pairs with thymine (A-T) and cytosine pairs with guanine (C-G). This pairing, maintained by hydrogen bonds, ensures the consistent spacing within the double helix structure, where adenine and guanine have a two-ring structure, and cytosine and thymine have a single ring structure. As a result, a one-ring molecule pairs with a two-ring molecule, keeping the distance between the two strands and the shape of the DNA molecule uniform.