Which part of the cell contains the genetic material?

The nucleus is the part of the cell that contains the genetic material, which is primarily in the form of DNA. This genetic material governs the cell's functions and is responsible for heredity, as it carries the instructions for making proteins and regulating cellular activities. The nucleus is surrounded by a double membrane called the nuclear envelope, which helps protect the DNA and regulates what can enter and exit the nucleus.

In contrast, the rough endoplasmic reticulum is involved in protein synthesis and processing but does not contain genetic material. The cytoplasm is the fluid within the cell that houses organelles and facilitates metabolic processes, but it does not contain the cell's genetic information. The plasma membrane, which surrounds the cell, serves as a barrier to control the movement of substances in and out of the cell, but it too does not contain genetic material. Thus, the nucleus stands out as the essential storage site for the cell's DNA, making it the correct answer.