What structure is characteristic of DNA in terms of its chains?

The classic structure of DNA is characterized by two chains of nucleotides that are wound together to form a double helix. These chains run in opposite directions, a trait referred to as antiparallel orientation. This means that one strand runs in a 5' to 3' direction while the other runs in a 3' to 5' direction. This orientation is crucial because it allows for the complementary base pairing between the nitrogenous bases on the two strands, enabling the double helix structure to maintain stability and integrity.

The antiparallel arrangement also plays a vital role in DNA replication and transcription processes. Enzymes involved in these processes read the strands in a specific direction, and the antiparallel framework is essential for these cellular mechanisms to function correctly. Thus, understanding that DNA consists of two chains that are oriented antiparallel is fundamental to grasping its structure and function in biological systems.