How is DNA structured?

DNA is characterized by its double helix structure, which consists of two strands of nucleotides that twist around each other. Each nucleotide in DNA is made up of a sugar molecule, a phosphate group, and a nitrogenous base. The sugar-phosphate backbone provides structural support, while the nitrogenous bases pair specifically (adenine with thymine and cytosine with guanine) through hydrogen bonds, forming the rungs of the helix.

The double helix design is essential because it allows DNA to be compactly stored within the cell nucleus while also providing a reliable mechanism for replication. The complementary nature of the base pairing ensures that genetic information can be accurately copied during cell division, which is crucial for the continuation of life.

In contrast, single strands of nucleotides do not represent the stable structure of DNA and lack the complementary pairing that is vital for maintaining genetic information. Linear proteins and RNA molecules, while essential in biological processes, do not describe the DNA structure itself. Therefore, the description of DNA as a double helix with sugar-phosphate backbones accurately captures its composition and structural configuration.