The part of a cell that contains the genetic material is the nucleus. This membrane-bound organelle houses the cell's DNA, which contains the instructions necessary for the growth, development, and functioning of an organism. The nucleus plays a crucial role in regulating gene expression and mediating the transmission of genetic information during cell division. In eukaryotic cells, the nucleus is essential for maintaining the integrity of genetic material and orchestrating cellular activities, while prokaryotic cells handle genetic information in a different manner.