The Cell Cycle and The Regulators Controlling This Process

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The cell cycle is the process in which a cell goes through leading to the duplication of its DNA and division to produce two daughter cells. It follows a cyclical structure that includes interphase and mitosis. The interphase is composed of three sub sets, and it is where the cell duplicates its DNA and grows in preparation for mitosis. Mitosis is the process where a eukaryotic cell divides all its organelles into two, making two daughter cells.

The first interphase is the G1 phase, furtherly known as gap phase one. During this phase the cell grows and prepares for DNA synthesis. The mitochondrion respiration provides the energy for the growth.

After the G1 phase the cell goes through the first checkpoint, the G1 checkpoint formally known as the restriction point. At this point, if there is damage to the DNA or other external factors it doesn’t progress to the next phase. Instead of moving onto the next phase, the cell is killed off before it is committed to the cell cycle.

The second interphase is the G2 phase, furtherly known as the synthesis phase. This phase is where the DNA duplication occurs, and all the chromosomes are replicated. DNA polymerase are used to synthesise the DNA molecules which are essential for the duplication.

After synthesis, the cell goes through the S checkpoint. This checkpoint ensures that all the chromosomes and DNA that have been replicated are not damaged, so the cell can go further to the third interphase.

The final interphase is the G2 phase, furtherly known as the gap two phase. During this phase the cell goes through further growth and preparation for mitosis. Biosynthesis occurs which involves the production of microtubules, which are required for the mitosis stage.

After going through the final interphase, the cell goes through the G2 checkpoint. This point certifies that the replicated DNA is not damaged and that all the chromosomes have been replicated. The cell is then suitable to go through the mitosis stage.

The mitosis stage is made up of three sub-stages, the prophase stage, the metaphase stage, the anaphase stage, and the telophase stage.

During the prophase, mediated by condensin complex, the chromatin condenses into the structure of chromosomes. This process is called chromatin condensation. The condensed, highly coiled chromosomes then move onto the metaphase, where they align in the middle of the cell then separate into two daughter cells. The daughter cells then go through the M checkpoint, at this point whether the sister chromatids are correctly attached to the spindle microtublues is determined, if they are attached properly the cell can the enter the anaphase. The two daughter cells move onto the next anaphase. In the anaphase all the chromatids separate and align with the spindle fibres. Then in the telophase, the cell membrane forms, the nucleoli appear, and all the other organelles. The two daughter cells are fully formed.

There is an additional stage to the cell cycle called the G0 stage. This is known as the resting phase and cells are said to be resting in this phase which may be reversible (quiescence) if they get a signal to divide or irreversible (senescence). The cells there are alive and carrying out their functions but aren’t preparing for division.

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