Some of the processes associated with the flow of genetic information in prokaryotes—especially bacteria such as E. coli—are tightly coupled so that ribosomes can begin translating an mRNA before it is completely transcribed. In contrast, organisms with a nucleus must, by definition, have their informational molecules in separate compartments. In terms of the Central Dogma, DNA is in the nucleus; its RNA must be in both the nucleus and the cytoplasm, and proteins must be made in the cytoplasm. After they are made, however, they can function in any part of the cell or be secreted. The fact that many organisms contain over a thousand times more DNA than do bacteria introduces a further complication. This information must be copied, localized, and expressed in a coordinated and regulated fashion.