Cell cycle phases

The cell cycle is the set of stages or Ordered phases of a cell during its division process. It begins with the duplication of genetic material within a stem cell and culminates with two genetically the same independent daughter cells (in the case of the mitotic cell cycle) or four independent daughter cells with half of the chromosomal load of its parent (in the case of the meiotic cell cycle).

The process is regulated by:

• Various enzymes
• Proteins
• Other compounds such as: kinases or kinases, cyclines and inhibitors.

Depending on the cell type, the cell cycle It can be called:

• Mitotic cycle or mitosis: It is the process through which somatic eukaryotic cells are divided. We can divide the mitotic cell cycle into four main phases: phase G1, phase S, phase G2 and phase M.
• Meiotic cycle or meiosis: It is the process that develops in the sexual glands to produce gametes or sex cells (ovules and sperm). This is the division of a diploid stem cell (with full chromosomal load 2N) to cause four daughters daughters (with half of the 1n ON chromosomal load). We can divide the meiotic cell cycle into three main phases: interface, meiosis 1 (which includes prophase i, metaphase I, anaphase I and telophase i) and meiosis 2 (which includes prophase II, metaphase II, anaphase II and telophase II).

If you want to know the difference between mitosis and meiosis, do not hesitate to read this article that we recommend.

Next we will explain in detail each of the phases that make up the mitotic cell cycle.

It is the larger phase. The cell is maintained in a basal state of operation and its nucleus is called the interface nucleus. In turn, it is divided into three phases:

• Phase G1: also called “GAP 1” or “Growth Phase 1”, is the phase between The end of one cycle and the beginning of another. It lasts between 6 and 12 hours and in it the cell prepares to divide by increasing its size, synthesizing protein, enzymes and RNA and performing some other metabolic processes. This is where cell differentiation occurs. At this point the cell has a chromosomal endowment 2n. Do not hesitate to take a look at this post of ecology see on the chromosomes: what are, types and parts to know more about the subject.
• Phase s: also called “synthesis phase” or “synthesis phase”, is where The cell doubles its material genetic to be able to give a complete copy of the genome to each of the daughter cells. The sister chromatids of the chromosomes are formed (which are the two identical chains of DNA that each one possesses) and the centers are doubled. It lasts between 10 and 12 hours, which is almost half of the total duration of the cell division of a typical mammal cell. At this point the cell has a 4N chromosomal endowment.
• G2 phase: also called “GAP 2” or “Growth Phase 2”, is the phase that precedes mitosis. Here the genetic material is condensed and organized, they are finished duplicating and reorganizing the organelles or organelles and proteins and specialized RNAs occur. This phase lasts between 3 and 4 hours.

Profase is the First phase of mitosis or “Phase M”. Is where the following processes occur:

• The chromosomes constituted during phase S They condense In the cell nucleus and the nucleolus disappears.
• The Centers are separated and They migrate to the opposite poles of the cell.
• Each centering is separated into an independent centriole: these begin to form the mitotic spindle or acromatic spindle in the cell cytoplasm. The mitotic spindle is a structure made up of microtubules to which the chromosomes will be anchored to be able to move to the center of the cell.
• The chromatin begins to group and form chromatids: Subsequently these chromatids are grouped to form chromosomes.
• The nuclear membrane begins to break.

Some authors consider that promising and metaphase are the same phase. If we consider the promise as an individual phase, we can say that it is characterized by:

• The wrapping or cell membrane dissolves full.
• The Chromosomes finish condensing and become easily distinguishable.
• The knetocoros appear.
• The microtubules of the mitotic spindle begin to invade the nuclear space and They get hooked to the cinetocoros.

During the metaphase each of The chromosomes who anchored the microtubules of the mitotic spindle They are transported to the metaphysical plate o Equatorial plane, an area of ​​the Ecuador of the cell. This is equidistant to the centers that are in the poles.

In anaphase The sister chromatids of duplicate chromosomes They separate completely and migrate to the respective opposite poles of the cell so that both daughter cells can inherit a copy of each chromosome. This occurs thanks to the fact that proteins cohesion that unite the sister chromatids already degrade the action of the microtubules or fibers of the mitotic spindle that are anchored to the komosome kneaders.

Once the complete chromosomes games are located in each of the poles of the cell, they lengthen and decompress again to adopt their old thread form. The mitotic spindle also disappears and the nucleolus and cell membrane of each new daughter cell is formed.

Some authors divide the telophase into telophase I and Telofase II; considering telopse II as cytokinesis.

To end the cycle, cell membranes of both daughter cells They finish closing and separate full. In the case of animal cells this occurs thanks to a contractile actin and myosin ring that strangles them or “pinch” until dividing them. In the plant cells a structure called cell plaque just in the middle of the two daughter cells is created. Each new daughter cell possesses:

• Own cell organelles
• Cytoplasm
• Core
• Cell membrane
• Complete chromosomes game

Many authors do not consider cytocinesis as a phase of the cell cycle because they believe it is an independent but necessary process that happens to the telophase or simply includes it in the telophase. Others consider that it is a phase of the cell division process that is not included in phase M.

After the cell cycle or cell reproduction process has been completed, the cell enters the G1 phase again to Repeat and perpetuate the cycle. Some cells experience a temporary post -mitting phase between cytocinesis and the G1 phase called “phase G0”. It occurs outside the cell cycle because the cell performs vital processes not involved with cell division.

Some cells remain permanently in the G0 phase. This is known as state of quiescence and occurs in cells that They do not have the ability to divide. An example of this are neurons.

After a cell has divided numerous times, it is aged and enters a state of senescence. Finally comes apoptosis or cell death.

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