Mitosis is a fundamental process in cell biology that allows eukaryotic cells to replicate in a precise and controlled manner. Throughout history, scientists have identified four key phases in the mitosis cycle: prophase, metaphase, anaphase, and telophase. These phases occur in an orderly and coordinated manner, ensuring that each daughter cell obtains an exact copy of the genetic material of the mother cell. In this article, we will explore in detail each of the four phases of mitosis and how cell duplication takes place.
1. Prophase
Prophase marks the beginning of mitosis and is the phase in which the chromosomes, previously duplicated during interphase, begin to condense and become visible under the microscope. In this stage, the nuclear envelope surrounding the cell nucleus disintegrates, allowing the chromosomes to disperse throughout the cytoplasm.
In addition, in prophase, each chromosome consists of two sister chromatids joined by a centromere. Centrioles, cellular structures involved in the formation of the mitotic spindle, migrate to opposite poles of the cell, establishing the ends of what will be the mitotic spindle.
• Main events of prophase:
- Condensation of chromosomes
- Disintegration of the nuclear envelope
- Migration of centrioles to opposite poles
2 . Metaphase
After prophase, the cell enters metaphase, characterized by the alignment of the duplicated chromosomes in the equatorial plane of the cell. At this point, the microtubules of the mitotic spindle attach to the centromeres of the chromosomes, forming a structure called the metaphase plate.
This arrangement of the chromosomes in the metaphase plate ensures that, during the next phase, each sister chromatid is distributed equally to the daughter cells. Metaphase is a critical time in mitosis, since any error in the alignment of chromosomes can result in aneuploidy, a genetic condition associated with chromosomal abnormalities.
• Main events of metaphase:
- Alignment of chromosomes in the equatorial plane
- Formation of the metaphase plate
- Union of microtubules to centromeres
Anaphase is the phase in which sister chromatids are separated and brought to opposite poles of the cell. This process of chromosome segregation is achieved thanks to the contraction of the microtubules of the mitotic spindle, which exert opposite forces on the sister chromosomes.
During anaphase, each chromatid is considered an independent chromosome and is guided towards one of the cell poles. The cell undergoes marked stretching due to the traction of the microtubules, ensuring that each daughter cell receives a complete and exact copy of the genetic material.
• Main events of anaphase:
- Separation of sister chromatids
- Conduction of chromatids towards opposite poles
- Stretching of the cell by forces of the mitotic spindle
4 . Telophase
In telophase, the cell begins the process of reversing the events that occurred in prophase and metaphase. The chromosomes decondense and become less visible, reestablishing their scattered network appearance in the cell nucleus. Simultaneously, a new nuclear envelope forms around each set of chromosomes at opposite poles of the cell.
In addition, during telophase, the final preparations for complete cell division occur, including the segregation of organelles and the reorganization of cellular structures. This process culminates in the formation of two daughter cells, each with its own nucleus containing an identical copy of the genetic material of the mother cell.
• Main events of telophase:
- Decondensation of chromosomes
- Formation of new nuclear envelope
- Final preparations for cell division
In conclusion, mitosis is a highly regulated process crucial for the growth, development and maintenance of multicellular organisms. Through the four phases described - prophase, metaphase, anaphase and telophase - cells manage to duplicate efficiently and ensure the integrity of their genetic material. Understanding in detail how cell duplication takes place allows us to appreciate the complexity and beauty of this fundamental process in cell biology.