Final answer:
The term 'antiparallel' in the context of DNA refers to the two strands running in opposite directions, with one strand oriented 5' to 3' and the other oriented 3' to 5'. This arrangement is essential for DNA replication and for the hydrogen bonding between nitrogenous base pairs adenine and thymine, and cytosine and guanine.
Step-by-step explanation:
When we describe DNA strands as being antiparallel, we mean that the two strands run in opposite directions. Specifically, one strand runs in a 5' to 3' direction, while the other runs in a 3' to 5' direction. This orientation is crucial for many processes, such as DNA replication, where enzymes read the strands in a specific direction.
In a DNA molecule, the backbone of each strand consists of alternating sugar (deoxyribose) and phosphate groups. Nitrogenous bases (adenine, thymine, cytosine, and guanine) are attached to the sugar molecules and face toward the interior of the helix. The bases form hydrogen bonds with their complementary bases on the opposite strand, with adenine pairing with thymine and cytosine pairing with guanine.
The antiparallel nature of DNA is key for base pairing and for enzymes that operate during DNA replication and transcription. To summarize, the term antiparallel refers to the opposite orientations of the two DNA strands, which is crucial for the function and structure of DNA.