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Binary fission, mitosis, and meiosis are the main forms of cell division. Binary fission and mitosis are types of asexual reproduction in which the parent cell divides to form two identical daughter cells. Meiosis, on the other hand, is a form of sexual reproduction in which a cell divides its genetic material between the two daughter cells.
The Main Difference Between Binary Fission and Mitosis
While both binary fission and mitosis are types of cell division that duplicate cells, fission primarily occurs in prokaryotes (bacteria), while mitosis occurs in eukaryotes (e.g., plant and animal cells).
Another way to look at it is that in binary fission cell that divide lack a nucleus, while in mitosis, the cell that divides does possess a nucleus. To get a better understanding of the processes, let's take a closer look at what's involved.
Prokaryotic vs. Eukaryotic Cells
Prokaryotes are simple cells that lack a nucleus and organelles. Their DNA consists of one or two circular chromosomes. Eukaryotes, in contrast, are complex cells that have a nucleus, organelles, and multiple linear chromosomes.
In both types of cells, DNA is copied and separated to form new cells in an organized manner. In both types of cells, cytoplasm is divided to form daughter cells via the process of cytokinesis. In both processes, if everything goes as planned, the daughter cells contain an exact copy of the parent cell's DNA.
In bacterial cells, the process is simpler, making fission faster than mitosis. Because a bacterial cell is a complete organism, fission is a form of reproduction. While there are some single-celled eukaryotic organisms, mitosis is most often used for growth and repair rather than reproduction.
While errors in replication in fission are a way to introduce genetic diversity in prokaryotes, errors in mitosis can cause serious problems in eukaryotes (e.g., cancer). Mitosis includes a checkpoint to make certain both copies of DNA are identical. Eukaryotes use meiosis and sexual reproduction to ensure genetic diversity.
Binary Fission Steps
While a bacterial cell lacks a nucleus, its genetic material is found within a special region of the cell called a nucleoid. Copying the round chromosome starts at a site called the origin of replication and moves in both directions, forming two replication sites. As the replication process progresses, the origins move apart and separate the chromosomes. The cell lengthens or elongates.
There are different forms of binary fission: The cell can divide across the transverse (short) axis, the longitudinal (long) axis, at a slant, or in another direction (simple fission). Cytokinesis pulls the cytoplasm toward the chromosomes.
When replication is complete, a dividing line-called a septum-forms, physically separating the cytoplasm of the cells. A cell wall then forms along the septum and the cell pinches in two, forming the daughter cells.
While it's easy to generalize and say binary fission only occurs in prokaryotes, this isn't exactly true. Certain organelles in eukaryotic cells, such as mitochondria, also divide by fission. Some eukaryotic cells can divide via fission. For example, algae and Sporozoa may divide via multiple fission in which several copies of a cell are made simultaneously.
Mitosis is part of the cell cycle. The process is much more involved than fission, reflecting the complex nature of eukaryotic cells. There are five phases: prophase, prometaphase, metaphase, anaphase, and telophase.
- The linear chromosomes replicate and condense early in mitosis, in prophase.
- In prometaphase, the nuclear membrane and nucleolus disintegrate. Fibers organize to form a structure called the mitotic spindle.
- Microtubules help align chromosomes on the spindle in metaphase. Molecular machinery checks the DNA to assure replicated chromosomes align toward the proper target cell.
- In anaphase, the spindle draws the two sets of chromosomes away from each other.
- In telophase, the spindles and chromosomes move to opposite sides of the cell, a nuclear membrane forms around each set of genetic material, cytokinesis splits the cytoplasm, and cell membrane separates the contents into two cells. The cell enters the non-dividing part of the cell cycle, which is called interphase.
Binary Fission Versus Mitosis
Cell division can be confusing, but similarities and differences between binary fission and mitosis can be summed up in one simple table:
|Asexual reproduction in which one organism (cell) divides to form two daughter organisms.||Asexual reproduction of cells, usually parts of complex organisms.|
|Occurs in prokaryotes. Some protists and eukaryotic organelles divide via fission.||Occurs in eukaryotes.|
|Primary function is reproduction.||Functions include reproduction, repair, and growth.|
|A simple, rapid process.||A complex process that requires more time than binary fission.|
|No spindle apparatus is formed. DNA attaches to the cell membrane prior to division.||A spindle apparatus is formed. DNA attaches to the spindle for division.|
|DNA replication and separation occur at the same time.||DNA replication is completed long before cell division.|
|Not completely reliable. Daughter cells sometimes get unequal numbers of chromosomes.||High fidelity replication in which chromosome number is maintained through a checkpoint at metaphase. Errors occur, but more rarely than in fission.|
|Uses cytokinesis to divide cytoplasm.||Uses cytokinesis to divide cytoplasm.|
Binary Fission vs. Mitosis: Key Takeaways
- Binary fission and mitosis are both forms of asexual reproduction in which a parent cell divides to form two identical daughter cells.
- Binary fission occurs primarily in prokaryotes (bacteria), while mitosis only occurs in eukaryotes (e.g., plant and animal cells).
- Binary fission is a simpler and faster process than mitosis.
- The third main form of cell division is meiosis. Meiosis only occurs in sex cells (gamete formation) and produces daughter cells with half of the chromosomes of the parent cell.
- Carlson, B. M. "Principals of Regenerative Biology." (p. 379) Elsevier Academic Press. 2007
- Maton, A.; Hopkins, J.J.; LaHart, S. Quon; Warner, D.; Wright, M.; Jill, D. "Cells: Building Blocks of Life." (pp. 70-74) Prentice-Hall. 1997