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Binary Fission
What is Binary Fission?
Binary fission is a type of asexual reproduction exhibited by prokaryotes and unicellular organisms. It results in two
daughter cells that are exact copies of the parent cell.
Before dividing, a prokaryotic cell grows until it becomes big enough to divide. Then the cell goes through a series of
steps in order to divide.
Steps of Binary Fission
Step # 1: Replication of DNA
Replication of DNA (genetic material) marks the start of the binary fission process. Replication of the cell’s DNA prior to
cell division is essential for the process of binary fission, as each new cell must have an accurate and complete copy of
the DNA in order to function properly. Although prokaryotic DNA often appears as a tangled mass, it is in fact organized
as a single, supercoiled circular chromosome.
Step # 2: Growth of Cell
The second step in binary fission is growth of the parent cell. After duplication of DNA, the parent cell is ready to
reproduce by binary fission process. As a preparatory step, it grows considerably and increases its size. At the same time,
the two circular DNA strands (chromosomes) migrate and attach themselves to the cell membrane at different sites.
Step # 3: Segregation of DNA
Following cell growth, the cell elongates (stretches out) and pulls in opposite directions. The cell membrane extends and
pinches inward. During this process, separation of the two DNA strands (chromosomes) takes place.
Step # 4: Splitting of Cells
The final binary fission step is splitting of the parent cell into two daughter cells, each having DNA material of its own.
This final step is called cytokinesis. Cytokinesis is the physical division of one cell into two cells. Cytokinesis begins with a
pinching in of the cell membrane. As the membrane pinches inward to divide the cytoplasm, new cell wall materials are
made and deposited along the line of cell division. Ultimately, two genetically identical cells with complete cell
membranes and cell walls are produced.
Most prokaryotic organisms have an optimum temperature range for cell growth. When environmental temperatures
are above or below the optimum, cell division tends to decrease. The rate of fission is also dependent on sufficient
nutrients in the environment. Under ideal environmental conditions, many prokaryotic species undergo binary fission at
a fairly rapid rate with generation times of one to several hours. This can lead to an astonishing growth in population
size over a relatively short period of time. In some instances, populations of prokaryotes may increase by a million or
even a billion fold in a matter of days.