The structure in the nucleus on which genes are carried is called a chromosome.

Here's a breakdown:

* Genes: Units of heredity that determine specific traits. They are segments of DNA.

* DNA: A long, complex molecule that carries genetic information.

* Chromosomes: Structures made up of tightly coiled DNA and proteins. They are organized units of DNA.

* Nucleus: The control center of a cell that contains the chromosomes.

So, genes are located on chromosomes, which are found within the nucleus.