What type of cell is characterized by the absence of a nucleus?

The correct answer is based on the fundamental distinction between two major types of cells: prokaryotic and eukaryotic. Prokaryotic cells are indeed characterized by the absence of a nucleus. Instead of being enclosed within a membrane-bound nucleus, the genetic material in prokaryotic cells is located in a region called the nucleoid, which is not separated from the rest of the cell by a membrane.

In addition to their lack of a nucleus, prokaryotic cells are generally simpler and smaller than eukaryotic cells. They also typically lack many of the membrane-bound organelles that are found in eukaryotic cells. This difference in cellular structure is a key feature that defines prokaryotes, which include bacteria and archaea.

Eukaryotic cells, on the other hand, contain a nucleus and are more complex, with various membrane-bound organelles. Multicellular organisms are primarily composed of eukaryotic cells. Viruses, while they may lack a cellular structure and can infect both prokaryotic and eukaryotic cells, do not fit into either category as living cells because they require a host cell for replication and do not possess cellular components, including a nucleus. Thus, the