Binary fission

Binary fission is the process of asexual cell division in prokaryotes and some eukaryotic organelles, such as mitochondria and peroxisomes. Mitosis is not possible in prokaryotes because of the absence of a nucleus and linear chromosomes with a defined centromere region.

The process itself involves DNA replication, from a single origin of replication, followed by attachment of each of the parent and replicated DNA molecules to a separate part of the cell membrane. The cell then elongates, causing the chromosomes to separate, and the membrane invaginates, pinching the cells off from one another in a similar fashion to eukaryotic cytokinesis. Division is directed by a bacterial protein called FtsZ, a homologue of tubulin, the protein that polymerises to form eukaryotic microtubules (which themselves are involved in eukaryotic cell division).

Although binary fission of eukaryotic organelles is well-understood, exactly how the organelles are allotted to each daughter cell of cytokinesis remains unclear.