There are various exceptions to the modern interpretation of the cell. Some scientists consider viruses as living things even though they are not made up of cells. Although viruses have several features of life, the definition of cell theory does not consider them alive. Moreover, the origin of the first cell is unknown. There were no pre-existing cells before the first one as the definition of the cell omits that aspect. Chloroplasts and mitochondria also have their own unique genetic material, and they reproduce independently.
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