Mitosis is an Example of Which Type of Process

Mitosis is an Example of Which Type of Process.

What Is Mitosis?

Mitosis cell division

Mitosis is a method of jail cell segmentation in which a cell divides and produces identical copies of itself.
(Epitome credit: Giovanni Cancemi | Shutterstock)

The primary mechanism by which organisms generate new cells is through prison cell division. During this process, a single “parent” cell will divide and produce identical “daughter” cells. In this way, the parent cell passes on its genetic material to each of its daughter cells. Offset, however, the cells must duplicate their DNA. Mitosis is the process by which a cell segregates its duplicated DNA, ultimately dividing its nucleus into two.

Cell division is a universal process among living organisms. In 1855, Rudolf Virchow, a High german researcher, made a central observation about all living creatures: every prison cell originates from some other cell, or “omnis cellula e cellula
,” in the original Latin, as author Myron Shultz recounts in a 2008 article in the periodical Emerging Infectious Diseases.

The mechanisms of cell division vary betwixt prokaryotes and eukaryotes. Prokaryotes are single-celled organisms, such as leaner and archaea. They have a simple internal structure with free-floating DNA. They use jail cell partition as a method of asexual reproduction, in which the genetic makeup of the parent and resulting offspring are the same. One common mechanism of asexual reproduction in prokaryotes is binary fission. During this process, the parent cell duplicates its DNA and increases the volume of its prison cell contents. Somewhen, a fissure emerges in the center of the prison cell, leading to the germination of two identical daughter cells.

The cells of eukaryotes, on the other paw, have an organized central compartment, called the nucleus, and other structures, such equally mitochondria and chloroplasts. Most eukaryotic cells carve up and produce identical copies of themselves by increasing their prison cell volume and duplicating their DNA through a series of defined phases known as the cell bike. Since their Dna is independent within the nucleus, they undergo nuclear division as well. “Mitosis is divers as the sectionalisation of a eukaryotic nucleus,” said G. Andrew Hoyt, a professor of biological science at Johns Hopkins Academy, “[though] many people use it to reverberate the whole cell cycle that is used for cell duplication.”

Similar prokaryotes, single-celled eukaryotes, such every bit amoeba and yeast, too employ cell partitioning as a method of asexual reproduction. For circuitous multicellular eukaryotes like plants and animals, cell division is necessary for growth and the repair of damaged tissues. Eukaryotic cells can likewise undergo a specialized form of prison cell division called meiosis, which is necessary to produce reproductive cells like sperm cells, egg cells and spores.

Stages of the eukaryotic cell cycle

The eukaryotic jail cell cycle is a series of well-defined and carefully timed events that allow a cell to grow and separate. According to Geoffery Cooper, writer of “The Cell: A Molecular Arroyo, 2nd Ed.” (Sinauer Assembly, 2000) most eukaryotic jail cell cycles have 4 stages:

G1 phase
(first gap phase): During this phase cells that are intended for mitosis, grow and carry out various metabolic activities.

S phase
(synthesis phase): During this phase, the cell duplicates its DNA. Eukaryotic Deoxyribonucleic acid is coiled around spherical histone proteins to create a rod-shaped structure called the chromosome. During the Due south phase, each chromosome generates its copy, or sister chromatid. The two sis chromatids fuse together at a bespeak called the centromere, and the complex resembles the shape of the letter “X.”

G2 phase
(second gap stage): During this phase the cell continues to grow and generate proteins necessary for mitosis.

(G1, South and G2 phases are collectively referred to every bit “interphase.”)

1000 phase
(mitosis): Mitosis involves the segregation of the sis chromatids. A construction of poly peptide filaments called the mitotic spindle hooks on to the centromere and begins to contract. This pulls the sis chromatids apart, slowly moving them to reverse poles of the cell. By the end of mitosis each pole of the prison cell has a complete set of chromosomes. The nuclear membrane reforms, and the cell divides in half, creating two identical girl cells.

Chromosomes, become highly compacted during mitosis, and tin can be clearly seen every bit dense structures under the microscope.

The resulting daughter cells can re-enter G1 phase but if they are destined to divide. Not all cells need to divide continuously. For example, human nerve cells stop dividing in adults. The cells of internal organs like the liver and kidney separate only when needed: to supplant expressionless or injured cells. Such types of cells enter the G0 phase (quiescent phase). They remain metabolically active and only move into the G1 phase of the cell bicycle when they receive the necessary molecular signals, according to Cooper.

The stages of mitosis

(Image credit: ellepigrafica Shutterstock)

Stages of mitosis

Mitosis is divided into four stages, according to course materials from the Academy of Illinois at Chicago. The characteristic stages are also seen in the second half of meiosis.

The duplicated chromosomes are compacted and tin be hands visualized every bit sister chromatids. The mitotic spindle, a network of protein filaments, emerges from structures called centrioles, positioned at either finish of the cell. The mitotic spindle is flexible and is made of microtubules, which are in turn made of the protein subunit, tubulin.

The nuclear membrane dissolves and the mitotic spindle latches on to the sis chromatids at the centromere. The mitotic spindle can now move the chromosomes around in the cell. “You tin brand an analogy to a girder that’s holding up a skyscraper,” said Hoyt. “Except the girder can assemble and disassemble very rapidly. They are structural elements that are extremely dynamic.” By the terminate of metaphase, all the chromosomes are aligned in the center of the prison cell.

The mitotic spindle contracts and pulls the sis chromatids apart. They begin to move to opposite ends of the jail cell.

The chromosomes reach either end of the cell. The nuclear membrane forms again and the cell trunk splits into two (cytokinesis).

At the end of mitosis, 1 cell produces two genetically identical daughter cells.

A powerful light microscope captures this scene from the process of mitosis.

(Paradigm credit: Jane Stout, research associate in the laboratory of Claire Walczak, Indiana University.)

Cell cycle regulation and cancer

The diverse events of the cell wheel are tightly regulated. If errors occur at any i stage, the jail cell tin end jail cell division from progressing. Such regulatory mechanisms are known as jail cell bike checkpoints, according to Cooper. There are three checkpoints within the G1, G2 and M phases. Damaged Deoxyribonucleic acid stops cell bicycle progression in the G1 stage, ensuring that an aberrant cell volition not be replicated. The G2 checkpoint responds to incorrectly duplicated, or damaged DNA. Information technology prevents cells from moving into the M phase until the DNA is replicated correctly, or until the impairment is repaired. The M phase checkpoint can halt the cell wheel in metaphase. It ensures that all the sister chromatids are properly hooked up to the mitotic spindle and that sister chromatids movement towards opposite ends of the jail cell.

“If things go wrong and are non corrected, yous end up with some cells that go extra chromosomes and some that are deficient,” Hoyt said. “Often those cells have a genotype[DNA sequence] that won’t support the life of the prison cell, and the will jail cell dice. That’s usually a good thing.”

Sometimes, abnormal cells manage not only to survive, only also to proliferate. Most often, these cells are implicated in cancer. “It [the cell] may have an extra re-create of a chromosome that has an oncogene on it. And that’due south going to start pushing the cell cycle forward when it shouldn’t be going frontward,” Hoyt said. “That’s a first step toward cancer progression.” Cancerous cells are known to go through rampant and unregulated cell divisions.

The relationship betwixt the prison cell cycle and cancer has led to the development of a course of cancer drugs that specifically target cancer cells during mitosis. According to anarticle published in 2012 in the journal Cell Death & Disease
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, “this strategy encompasses a prolonged arrest of cells in mitosis, culminating in mitotic cell death.”

For example, microtubule poisons stop mitosis by targetingmicrotubules
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, the master component of the mitotic spindle. Dissentious these thin, hollow, microscopic poly peptide filaments ultimately prevents sister chromatids from beingness pulled apart. Examples of microtubule poisons are the medications paclitaxel (Taxol) and vinca alkaloids, which are used to treat a range of cancers, including certain ovarian and breast cancers.

All the same, microtubule poisons are not without their limitations. According to a 2018 review article published in the journal EMBO Reports, these drugs tin can sometimes be toxic to brain cells, or cancer cells tin become drug-resistant and avoid being killed. In an effort to find alternate solutions, researchers are looking to develop drugs that target other aspects of mitosis. In 2016, the Food and Drug Administration (FDA) approved the use of the new drug Palbociclib in combination with existing anti-cancer drugs to treat certain breast cancers. Palbociclib works by keeping cancer cells frozen in the G1 stage, according to a 2017 review article published in the journal Nature Reviews Cancer
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The compounds tested in clinical trials so far have had some success but accept non been as effective as microtubule poisons, co-ordinate to EMBO Reports. Nevertheless, targeting mitosis in the treatment of cancer remains an active surface area of research.

Additional resources

  • The Biology Project (Academy of Arizona): The Cell Bike & Mitosis Tutorial
  • Mitosis — When Cells Divide Autonomously
  • Scitable (Nature): Mitosis
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Aparna Vidyasagar is a freelance science announcer who specializes in wellness and life sciences. Aparna has written for a number of publications, including New Scientist, Science, PBS SoCal, Mental Floss, and several others. Aparna has a doctorate in Cellular and Molecular Pathology from the Academy of Wisconsin-Madison, and as well received a chief’s caste and bachelor’s caste from the same university.

Mitosis is an Example of Which Type of Process