<P> A prokaryote is a unicellular organism that lacks a membrane - bound nucleus, mitochondria, or any other membrane - bound organelle . The word prokaryote comes from the Greek πρό (pro) "before" and κάρυον (karyon) "nut or kernel". Prokaryotes are divided into two domains, Archaea and Bacteria . In contrast, species with nuclei and organelles are placed in the third domain, Eukaryota. . Prokaryotes reproduce without fusion of gametes . The first living organisms are thought to have been prokaryotes . </P> <P> In the prokaryotes, all the intracellular water - soluble components (proteins, DNA and metabolites) are located together in the cytoplasm enclosed by the cell membrane, rather than in separate cellular compartments . Bacteria, however, do possess protein - based bacterial microcompartments, which are thought to act as primitive organelles enclosed in protein shells . Some prokaryotes, such as cyanobacteria may form large colonies . Others, such as myxobacteria, have multicellular stages in their life cycles . </P> <P> Molecular studies have provided insight into the evolution and interrelationships of the three domains of biological species . Eukaryotes are organisms, including humans, whose cells have a well defined membrane - bound nucleus (containing chromosomal DNA) and organelles . The division between prokaryotes and eukaryotes reflects the existence of two very different levels of cellular organization . Distinctive types of prokaryotes include extremophiles and methanogens; these are common in some extreme environments . </P>

Where is the genetic information found in a prokaryotic cell