The long molecules of DNA that are usually found in pairs are called chromosomes.

Here's why:

* DNA Structure: DNA is a long, double-stranded molecule that resembles a twisted ladder.

* Chromosomes: Chromosomes are made up of tightly coiled strands of DNA. Each chromosome is actually two identical DNA molecules (called sister chromatids) joined together at a point called the centromere.

* Pairs: Humans have 23 pairs of chromosomes (46 total), with one chromosome from each pair inherited from the mother and the other from the father.

So, while DNA itself is a long molecule, it's organized into chromosomes, which are the paired structures we usually talk about in the context of genetics.