Final answer:
The nucleus is the organelle found in eukaryotic cells that confines the chromosomes, separating the genetic material from the rest of the cell and playing a key role in gene regulation and cell division.
Step-by-step explanation:
The organelle in question is the nucleus. In eukaryotic cells, which are cells that possess a membrane-bound nucleus and organelles, the nucleus is crucial for housing the chromosomes and, therefore, the cell's genetic material. It separates the DNA from the rest of the cell cytoplasm. The nucleus is surrounded by a complex nuclear envelope, which includes nuclear pores allowing the transport of molecules like RNA out to the cytoplasm. The interior of the nucleus contains a substance called nucleoplasm and also features the nucleolus, where ribosomal RNA (rRNA) synthesis occurs.
The organization and packing of eukaryotic DNA within the nucleus ensure that the long DNA molecules are compacted into structures called chromosomes. This is achieved by wrapping the DNA around proteins known as histones. During the cell cycle, the nucleus plays a central role in cell division, particularly during the processes of mitosis and meiosis, where chromosomal DNA is replicated and sorted into daughter cells.
The presence of a nucleus is what distinguishes eukaryotic cells from prokaryotic cells, which lack a membrane-bound nucleus. In prokaryotes, the DNA is contained within the nucleoid region instead. The structural organization of the nucleus ensures the efficient regulation of gene expression and genetic integrity, making it an essential component of eukaryotic cellular organization.