membrane. The bacterial genome is smaller than that of a eukaryote. For example, E. coli has only 4.6 million base pairs of DNA, versus three billion in humans. As in eukaryotes, the DNA is tightly coiled to fit it into the cell. Unlike eukaryotes, however, the DNA is not attached to histone proteins.

Much of what we know about DNA replication has come from study of bacteria, particularly E. coli, and the details of this process are discussed elsewhere in this encyclopedia. Unlike eukaryotic replication, prokaryotic replication begins at a single point, and proceeds around the circle in both directions. The result is two circular chromosomes, which are separated during cell division. Plasmids replicate by a similar process.

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