10.3
Binary Fission
Prokaryotes propagate via cell division, albeit by using a different process than eukaryotes, one that's asexual, forming two genetically identical clones of itself. This type of reproduction is termed binary fission, meaning division in half.
To divide, the cell first replaces its DNA, copying the chromosome from its origin of replication, an area near chromosomal contact with the cell plasma membrane. Replication enzymes copy the chromosome bidirectionally, moving in opposite directions from the origin to create two double-stranded chromosomes.
As replication occurs, both chromosomes begin to move away from each other, to opposite sides of the cell. The cell itself lengthens, spurring chromosomal or nucleoid separation.
Once the chromosomes have moved to opposite sides, cytoplasmic separation, cytokinesis can begin. Now a ring of self-assembling proteins forms at the cell midpoint, directing the formation of a septum ring, a developing cell wall from the midpoint peripheries to the middle.
When the septum is finished developing, it pinches off the cell, splitting to yield two identical daughter cells.
Fission is the division of a single entity into two or more parts, which regenerate into separate entities that resemble the original. Organisms in the Archaea and Bacteria domains reproduce using binary fission, in which a parent cell splits into two parts that can each grow to the size of the original parent cell. This asexual method of reproduction produces cells that are all genetically identical.
The speed of Bacterial Fission
Though its speed varies among species, binary fission is generally rapid and can yield staggering growth. In the amount of time it takes bacterial cells to undergo binary fission, the number of cells in the bacterial culture doubles. Thus, this period is the doubling time. For example, Escherichia coli cells typically divide every 20 minutes. Bacterial growth, however, is limited by factors including nutrient and space availability. Thus, binary fission occurs at much lower rates in bacterial cultures that have encountered a growth-limiting factor (i.e., entered a stationary growth phase).
Fission of Organelles in Eukaryotic Cells
In addition to organisms in the Archaea and Bacteria domains, some organelles in eukaryotic cells also reproduce via binary fission. Mitochondria, for example, divide by prokaryotic binary fission. This process requires the division of mitochondrial proteins and DNA.
Prokaryotes propagate via cell division, albeit by using a different process than eukaryotes, one that's asexual, forming two genetically identical clones of itself. This type of reproduction is termed binary fission, meaning division in half.
To divide, the cell first replaces its DNA, copying the chromosome from its origin of replication, an area near chromosomal contact with the cell plasma membrane. Replication enzymes copy the chromosome bidirectionally, moving in opposite directions from the origin to create two double-stranded chromosomes.
As replication occurs, both chromosomes begin to move away from each other, to opposite sides of the cell. The cell itself lengthens, spurring chromosomal or nucleoid separation.
Once the chromosomes have moved to opposite sides, cytoplasmic separation, cytokinesis can begin. Now a ring of self-assembling proteins forms at the cell midpoint, directing the formation of a septum ring, a developing cell wall from the midpoint peripheries to the middle.
When the septum is finished developing, it pinches off the cell, splitting to yield two identical daughter cells.
From Chapter 10:
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10.3 : Binary Fission
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