All the DNA in one cell of an organism is called its genome.

Here's a breakdown:

* Genome: The complete set of genetic instructions for an organism, including all the DNA within its cells.

* DNA: Deoxyribonucleic acid, the molecule that carries genetic information.

* Cell: The basic structural and functional unit of all living organisms.

So, the genome is the sum total of all the DNA found within a single cell, which contains the blueprint for the entire organism.