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Binary fission is the form of asexual reproduction and cell division used by prokaryotic organisms (such as bacteria or archaea). This process results in the reproduction of a living prokaryotic cell by division into two parts which each have the potential to grow to the size of the original cell
Mitosis and cytokinesis are not the same as binary fission. The ability of some multicellular animals, such as echinoderms and flatworms, to regenerate two whole organisms after having been cut in half, is also not the same as binary fission. Neither is vegetative reproduction of plants.
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Binary fission is asexual; the organism splits directly into two equal-sized offspring, each with a copy of the parent's genetic material. Binary fission is the usual type of reproduction in prokaryotes, the more familiar of which are known as bacteria.
Organisms that reproduce through binary fission generally have exponential growth phases. Escherichia coli cells are able to divide every 20 minutes under optimum conditions.
Binary fission begins with DNA replication. DNA replication starts from an origin of replication, which opens up into a replication bubble (note: prokaryotic DNA replication usually has only 1 origin of replication, whereas eukaryotes have multiple origins of replication). The replication bubble separates the DNA double strand, each strand acts as template for synthesis of a daughter strand by semiconservative replication, until the entire prokaryotic DNA is duplicated.
After this replicational process, cell growth occurs.
Each circular DNA strand then attaches to the cell membrane. The cell elongates, causing the two chromosomes to separate.
Cell division in bacteria is controlled by the septal ring, a collection of about a dozen proteins that collect around the site of division. There, they direct assembly of the division septum. The cell wall and plasma membrane starts growing transversely from near the middle of the dividing cell. This separates the parent cell into two nearly equal daughter cells, each having a nuclear body [1]
The cell membrane then invaginates (grows inwards) and splits the cell into two daughter cells, separated by a newly grown cell plate.
Eukaryotic organelles such as mitochondria and chloroplasts also reproduce within the eukaryotic cell by binary fission. How they are allotted to one descendant cell or the other during mitosis and cytokinesis is not yet clear.