DNA is a long, complex molecule that contains the genetic instructions for building and maintaining an organism. It's organized into structures called chromosomes, and each gene occupies a specific location on a chromosome.

Here's a breakdown:

* DNA: The fundamental building block of genes, containing the genetic code.

* Genes: Segments of DNA that carry the instructions for building specific proteins.

* Chromosomes: Structures made of DNA and proteins that carry genes.

* Proteins: The molecules that carry out most of the functions in a living organism, based on instructions from genes.