What is Mitosis?
Cell division is the driving process of reproduction at the cellular level. Most eukaryotic cells divide in a manner where the ploidy or the number of chromosomes remains conserved, except in the case of germ cells where the number of chromosomes is halved. Let’s see different phases of Mitosis.
Mitosis is the phase of the cell cycle where the nucleus of a cell is divided into two nuclei with an equal amount of genetic material in both the daughter nuclei. It succeeds the G2 phase and is succeeded by cytoplasmic division after the separation of the nucleus. The processes occurring during mitosis are trying to separate from each other but for the convenience of understanding, it has been divided into the following stages which are explained below.
The 4 Stages of Mitosis
Right before prophase, the cell spends most of its lifetime in the interphase, where preparations are made before the beginning of mitosis (the DNA is copied). However, since the actual process involves the division of the nucleus, prophase is technically the first stage of this process.
The different phases of Mitosis occurring during cell division are given as follows-
Prophase immediately follows S and G2 phase of the cycle and is marked by condensation of the genetic material to form compact mitotic chromosomes composed of two chromatids attached at the centromere. The completion of prophase is characterized by the initiation of the assembly of the mitotic spindle, the microtubules, and the proteinaceous components of cytoplasm that help in the process. The nuclear envelope starts disintegrating.
Prophase: The first phase of mitosis
The nuclear envelope completely disintegrates at the onset of metaphase and the condensed chromosomes spread throughout the cytoplasm. These chromosomes are composed of two sister chromatids held at the centre by centromeres. The spindle fibres attach to a disc-like structure at the surface of centromeres, known as kinetochores. The spindle fibres from one centriole attach to only one sister chromatid. The chromosomes aligned along the equator of the cytoplasm, an arrangement characteristic of metaphase known as the metaphase plate.
Metaphase: The nucleus breaks down and the chromosomes begin to move
The onset of anaphase is marked by the splitting of the sister chromatids. These sister chromatids become the chromosome of the daughter nuclei. The chromosomes are then pulled towards the pole by the fibres attached to the kinetochores of each chromosome. The centromere of each chromosome leads at the edge while the arms trail behind it.
Anaphase: Segregation of chromosomes to opposite ends of the cell
The chromosomes that cluster at the two poles start coalescing into an undifferentiated mass, as the nuclear envelope starts forming around it. The nucleolus, Golgi bodies and ER complex, which had disappeared at the completion of prophase start to reappear.
Telophase: Final stage of mitosis
Telophase is followed by cytokinesis, which denotes the division of the cytoplasm to form two daughter cells. Thus, it marks the completion of cell division.
1. What is Mitosis?
Mitosis is a type of cell division that results in the development of two daughter cells, each possessing the same type and number of chromosomes as their original parent nucleus. This type of cell division is observed in non-sex cells, essentially growing body parts and repairing damaged tissues.
2. Name the 4 stages of mitosis.
The 4 stages of mitosis are:
3. What is prophase?
The process of mitosis begins with the prophase. In this stage, the chromatin condenses and the nucleolus disappears.
4. What happens in metaphase?
The second stage of the process, the parent cell contains chromosomes that are condensed and present at the equator, before being split apart for each of the two daughter cells.
5. Explain anaphase.
The anaphase is marked by the splitting of the sister chromatids. Eventually, these sister chromatids become the chromosome of the daughter nuclei.
6. List the events of telophase.
The final stage of mitosis, telophase involves the now spilt sister chromatids reaching the polar ends. The nuclear envelope starts forming along with the other cell organelles such as the Golgi bodies and ER complex.
Explore more details about mitosis cell division, mitosis diagram and more, only on BYJU’S Biology.