Here's why:

* Chromosomes are long, thread-like structures made up of DNA and proteins.

* DNA contains the genetic instructions for an organism.

* Genes are specific segments of DNA that code for a particular trait or characteristic.

Think of it like this:

* A chromosome is like a book.

* A gene is like a chapter in that book.

* The whole book contains all the instructions, and each chapter focuses on a specific aspect.

So, while chromosomes are the structures that carry the genetic information, genes are the functional units within those structures that determine specific traits.