Here's a breakdown:

* Chromosome: A long, thread-like structure made of DNA that carries genetic information.

* DNA (Deoxyribonucleic acid): A molecule that contains the genetic instructions for an organism.

* Gene: A segment of DNA that contains the instructions for building a specific protein or RNA molecule.

Think of it like this:

* Chromosome: A book containing all the information about an organism.

* DNA: The text within the book.

* Gene: A single paragraph or chapter within the book, containing instructions for making something specific.

So, the DNA code on a chromosome is a series of genes, each containing instructions for building a particular protein or RNA molecule. These proteins and RNA molecules are essential for all the functions of a living organism.