Mitosis is a type of cell division that results in the formation of two identical daughter cells from a single parent cell.Â
Mitosis can be divided into four main phases and here comes the question of which of these phases encompasses all of the stages of Mitosis but no other events.
This process is essential for the growth and development of many organisms, as it allows cells to divide and proliferate to form new tissues and organs.
In humans, mitosis is the primary means by which cells are replicated. The process of mitosis typically involves a series of events that include the segregation of chromosomes into two daughter cells.
During mitosis, chromosomes condense and segregate into discrete portions called chromatids.
Which Of These Phases Encompasses All Of The Stages Of Mitosis But No Other Events?
The answer to this question is Prophase encompasses all of the stages of mitosis.
This is because prophase is the longest stage of all the other stages of mitosis and of the four main phases of the cell cycle prophase is the only one that encompasses all of the stages of mitosis but no other events.
The other three phases each include additional events beyond those associated with mitosis.
Prophase is the first of three phases of mitosis, along with prometaphase and metaphase.
Prophase begins when the chromosomes condense in the center of the cell, at which point they are called nuclei.
Prophase is divided into three substages: prometaphase, metaphase, and anaphase. These substages are also referred to as prophase I, II, and III.
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Phases Of Mitosis
There are 6 phases of mitosis and these phases are characterized by different events that occur within the cell, such as the condensation of chromosomes and the separation of the duplicated chromosomes
1. Prophase
In prophase, the chromosomes condense and become visible. The nuclear envelope breaks down, and the spindle apparatus forms.
Prophase lasts about 15 minutes in animal cells and 50 minutes in plant cells.
In prophase I of meiosis, homologous chromosomes pair up and exchange genetic information.
This process is called crossing over. Prophase I also includes the formation of the spindle apparatus and the breakdown of the nuclear envelope.
Depending on the cell type, prophase I can last anywhere from several hours to days.
Prophase II is relatively short, lasting only 10-30 minutes. In this phase, the sister chromatids separate and move to opposite poles of the cell.
2. Prometaphase
In the cell cycle, prometaphase is the phase in which the chromatids of each chromosome are separated.
This phase begins with the breakdown of the nuclear envelope and ends with the formation of the mitotic spindle.
Prometaphase is followed by metaphase, during which time the chromosomes line up in the middle of the cell, and anaphase, during which time they are pulled apart to opposite sides of the cell.
During prometaphase, a number of things happen in preparation for mitosis. The chromosomes uncoil and become more visible as they condense.
The nuclear envelope breaks down so that the chromosomes can move freely within the nucleus.
Microtubules from opposite poles of the cell begin to attach to each chromatid at a point called the kinetochore.
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3. Metaphase
Metaphase is the third stage of mitosis, during which the chromosomes line up in the middle of the cell and are attached to the spindle fibers.
This stage begins when the chromosomes reach the equator of the cell and lasts until they are pulled to opposite poles.
In animal cells, metaphase is often divided into two subphrases: prometaphase and metaphase.
Prometaphase is characterized by the breakdown of the nuclear envelope and the attachment of the chromosomes to the spindle fibers.
Metaphase I, on the other hand, is characterized by the alignment of homologous chromosomes in pairs along the equator.
4. Anaphase
Anaphase is the stage of mitosis in which chromosomes are separated and moved to opposite sides of the cell.
This stage begins when the spindle fibers that were attached to the chromosomes during prophase begin to pull them apart.
The centromeres that connect the two sister chromatids split, and the chromatids are pulled to opposite sides of the cell by the spindle fibers.
As they are pulled apart, the chromatids shorten and thicken, becoming visible as chromosomes.
During anaphase, the chromosomes continue to move towards opposite poles of the cell.
As they reach the poles, they begin to elongate and thin out, eventually disappearing from view.
The final stage of anaphase is telophase, in which the chromosomes arrive at their respective poles and decondense, becoming indistinguishable from one another once again.
5. Telophase
Telophase is another phase of mitosis, during which the chromosomes arrive at the opposite poles of the cell and decondense.
A new nuclear envelope forms around each set of chromosomes, and the nucleolus reappears.
The cytoplasm begins to contract, and the cell begins to pinch in at the center, forming a cleavage furrow. Finally, the cell divides into two daughter cells.
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6. Cytokinesis
Cytokinesis is the last step of cell division, where the cytoplasm of the cell is divided into two equal parts.
This process begins during telophase, when the chromosomes start to separate and move to opposite sides of the cell.
The next step is for a thin layer of membrane, called the cleavage furrow, to form around the center of the cell. This furrow deepens and pinches the cell in two, creating two new cells.
Cytokinesis is a vital process for ensuring that each new cell has an equal amount of cytoplasm and organelles.
without cytokinesis, one cell would end up with all of the organelles and twice as much cytoplasm as the other.
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Conclusion
The answer to the question posed in the title of this article is that prophase encompasses all of the phases of nuclear division but none of the other events that accompany cell division.
