The precise timing and formation of the mitotic spindle is critical to the success of eukaryotic cell division. (credit: modification of work by “Mcstrother”/Wikimedia Commons) Figure 6.9 The binary fission of a bacterium is outlined in five steps. When the new cell walls are in place, the daughter cells separate. A septum is formed between the nucleoids from the periphery toward the center of the cell. After the chromosomes have cleared the midpoint of the elongated cell, cytoplasmic separation begins.

As the cell elongates, the growing membrane aids in the transport of the chromosomes. As the new double strands are formed, each origin point moves away from the cell-wall attachment toward opposite ends of the cell. Replication of the DNA is bidirectional-moving away from the origin on both strands of the DNA loop simultaneously. The starting point of replication, the origin, is close to the binding site of the chromosome to the plasma membrane ( Figure 6.9). The packing proteins of bacteria are, however, related to some of the proteins involved in the chromosome compaction of eukaryotes. As in eukaryotes, the DNA of the nucleoid is associated with proteins that aid in packaging the molecule into a compact size. The single, circular DNA chromosome of bacteria is not enclosed in a nucleus, but instead occupies a specific location, the nucleoid, within the cell. Because of the speed of bacterial cell division, populations of bacteria can grow very rapidly.

The cell division process of prokaryotes, called binary fission, is a less complicated and much quicker process than cell division in eukaryotes. This type of cell division is called binary fission. Mitosis is unnecessary because there is no nucleus or multiple chromosomes. In bacterial cells, the genome consists of a single, circular DNA chromosome therefore, the process of cell division is simplified. The genomic DNA must be replicated and then allocated into the daughter cells the cytoplasmic contents must also be divided to give both new cells the machinery to sustain life. To achieve the outcome of identical daughter cells, some steps are essential. In unicellular organisms, daughter cells are individuals. In both prokaryotic and eukaryotic cells, the outcome of cell reproduction is a pair of daughter cells that are genetically identical to the parent cell. For unicellular organisms, cell division is the only method to produce new individuals. Prokaryotes such as bacteria propagate by binary fission. Explain how FtsZ and tubulin proteins are examples of homology.Describe the process of binary fission in prokaryotes.By the end of this section, you will be able to:

Binary fission examples animals