The brain of a cell, which contains DNA, is called the nucleus.

Here's why:

* DNA is the cell's blueprint: DNA contains the genetic instructions for the cell's structure and function.

* The nucleus protects DNA: The nucleus is a membrane-bound organelle that houses the DNA, keeping it safe and organized.

* The nucleus controls cell activity: The DNA within the nucleus directs the production of proteins, which carry out the cell's functions.

So, the nucleus is like the control center of the cell, and the DNA within it is the instruction manual.