Final answer:
The nucleus is the structure in a eukaryotic cell where DNA is contained. It is surrounded by a double membrane called the nuclear envelope and contains chromatin and nucleoli for organizing DNA and synthesizing ribosomal RNA.
Step-by-step explanation:
In eukaryotic cells, DNA is contained within the nucleus. The nucleus is an organelle that is surrounded by a complex double membrane called the nuclear envelope, which contains nuclear pores to regulate the transport of materials. The nucleus plays a crucial role in regulating the cell's activities and is essential in reproduction and heredity. Eukaryotic DNA is organized into multiple linear chromosomes and is associated with histone proteins to help condense and organize the DNA within the nucleus.
During cell division, the chromatin in the nucleus coils tightly to form chromosomes. The nucleus also contains one or more nucleoli, where the RNA components of ribosomes are synthesized. As the central repository for genetic information, the nucleus is distinct from organelles such as the endoplasmic reticulum and Golgi apparatus, and it is different from structures such as cilia, which play roles in cell movement and function.