What does the term 'complementary' refer to in DNA structure?

In the context of DNA structure, the term 'complementary' specifically refers to the base pairing between nucleotides. DNA is composed of two strands that run in opposite directions, and the nucleotides on one strand are paired with specific nucleotides on the other strand. This pairing is based on the rules of complementary base pairing: adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C).

This specific pairing is crucial for the fidelity of DNA replication and transcription, as it ensures that the genetic information is accurately passed on during cell division. Each base on one strand is complemented by its partner on the opposite strand, forming a base pair that contributes to the overall stability and structure of the DNA double helix. Understanding this complementary nature is fundamental to molecular biology and genetics, as it underpins many processes, including replication and gene expression.