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The nucleus is an important feature of a eukaryotic cell. The nucleus is usually round and stores long coiled structures called chromosomes, which contain the cell’s genetic material.

A prokaryotic cell, by contrast, doesn’t have a nucleus. Instead, its chromosomes are loose in the cell, not surrounded by a membrane. Because prokaryotic cells lack nuclei and other membrane-bound structures, prokaryotic cells are typically simpler than eukaryotic cells.