Everyone knows that cells make up every living creature, but how does one cell become many cells to create tissue, organs, and even people? How did our body make the around 37.2 trillion cells?
To go beyond a single cell, cells need to reproduce, and almost all cells accomplish this through a process called “mitosis” or “meiosis.” In mitosis, a cell divides to create two identical copies of itself.
Meiosis is a similar situation, except that in the division process, it creates four new cells and each new cell has only half of the DNA of the original cell; in other words, meiosis doesn’t create exact copies of the original cell.
This may sound like a simple explanation, but it’s really a very complex condition, and the cell does a lot of hard work to accomplish mitosis and meiosis.
Every day we have cells that get old and die and our bodies need to make new ones to replace them.
It’s important to note that there is another method of cell development. For simpler organisms such as bacteria, those cells use a process called binary fusion.
It may not be as complex as both mitosis and meiosis, but it’s still a lot of work. Each cell division type depends on the creature as well as the purpose of the cell.
This cell division type is due to a need for an exact copy of the cell type. Cells such as blood, skin, and even your muscles need to have exact duplicates.
All of the contents of the original cell are copied, including the genetic coding, functions, and DNA. The original cell is called the “mother cell” and the new cells are called “daughter cells.”
Watching a cell go through the mitosis process is pretty astounding. There are five phases of a cell cycle and it begins with the “normal” state and then continues to the “interphase” state.
The interphase state is when the cell gets a signal that it needs to duplicate itself and it then goes to the second state which is called “prophase.”
Prophase prepares the cell to replicate itself. It requires that the nuclear membrane and nucleus breaks down so that it can transfer materials to the new cell, and the chromatin inside is required to condense to become chromosomes.
From this point on cell division looks like a kind of dance.
The next move in mitosis is called the “metaphase” and under a microscope you would see the chromosomes move to the middle of the cell and line up.
They are connected together with “spindle fibers” which are long strands.
In the “anaphase” stage, the chromosomes separate and relocate to the opposite sides of the cell.
Now that there are two of everything, the cell needs to create two nuclear membranes to hold and protect them. This is called the “telophase.” Once the new membranes encircle each set of chromosomes, they begin to uncoil and the cell walls in the middle start to “pinch” in a process called cell cleavage or “cytokinesis” so that it closes off and creates two new cells.
The two new cells that result from mitosis are called “diploids.”
Unlike mitosis where only the cell is being created, meiosis is a situation that is used when there is a requirement for reproduction of the entire organism.
Meiosis has two separate divisions, resulting in four new cells and each cell contains only half of the original DNA. This is really important because it allows for the combination of new genetic material to be contributed by other creatures and this allows for healthy varieties of life.
The resulting cells after meiosis are called “haploids;” an easier name to remember because they have only half of the original DNA. An example of cells that go through meiosis are those that are used in sexual reproduction. These go by the name of “gametes.”
Unlike complex creatures, the simplest of organisms don’t require mitosis or meiosis. Organisms such as bacteria make use of “binary fission” for cell division.
In this process the DNA not only makes a copy of itself, but the cell begins to grow to twice its size. Since there are now two copies of the DNA each one moves to the cell’s opposite side and then the cell wall begins to pinch-off in the middle so that it creates two completely separate cells.
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