What describes the arrangement of DNA strands that run in opposite directions?

The term "antiparallel" refers to the unique structural arrangement of double-stranded DNA, where each strand runs in opposite directions. In this configuration, one strand has a directionality from the 5' to 3' end, while the opposite strand runs from 3' to 5'. This orientation is crucial for the processes of DNA replication and transcription, as enzymes that interact with DNA, such as DNA polymerase, can only synthesize DNA in the 5' to 3' direction.

Understanding the antiparallel arrangement is fundamental for grasping how the two strands of the double helix work together: the complementary base pairing that occurs between adenine and thymine, and between cytosine and guanine, is facilitated by this orientation. Overall, the antiparallel structure is a defining characteristic of DNA that enables its stability and functionality.