Maintaining Chromosome Stability Through Mitosis
Mitosis is a critical form of cell division that ensures the preservation of the same number of chromosomes in daughter cells as in parent cells. While there are minor distinctions in mitosis between animals and plants, the fundamental stages remain consistent.
Key Points:
- Mitosis is an ongoing process that occurs in both haploid and diploid cells throughout the body.
- Mitosis consists of two major stages: Karyokinesis and Cytokinesis.
- Nucleus Division (Karyokinesis)
- Karyokinesis, or nucleus division, is a pivotal step in mitosis.
Formation of the Mitotic Apparatus:
1. Centriole Replication: During interphase, centrioles duplicate. Each pair of centrioles is situated within the same chromosome.
2. Centriole Separation: At the initiation of Karyokinesis, these centriole pairs divide and migrate to opposite sides of the nucleus. This separation establishes the "pole polarity" of the dividing cells.
3. Microtubule Formation: From each pair of centrioles, sets of microtubules form. Composed of the protein "tubulin" and containing traces of RNA, these microtubules give rise to astral microtubules and radiate outward to create the spindle.
4. Spindle-Kinetochore Complex: Additionally, two additional sets of microtubules form the spindle-kinetochore complex, an essential component for chromosomal segregation.
Understanding these processes provides valuable insights into the intricate mechanics of mitosis, crucial for maintaining genetic stability in living organisms.
Mitotic Apparatus Organisation and Karyokinesis Subdivision
The mitotic apparatus, which is made up of numerous kinds of spindle microtubules,
is essential for cell division.
1. Kinetochore Microtubules
These microtubules bind to chromosomes directly at specialized structures
known as kinetochores.
2. Polar Microtubules:
Polar microtubules do not directly interact with chromosomes.
They instead interact with polar microtubules from the opposite pole.
Mitotic Apparatus Functions:The spindle microtubules that comprise the mitotic apparatus are bigger than the
nucleus and serve vital functions during cell division. They are in charge of attaching and trapping chromosomes in order to ensure their alignment and ultimate equitable distribution across daughter cells.
Prophase is a Karyokinesis subdivision.
Prophase is the first phase of cell division and the first stage of mitotic karyokinesis.
Notably, even with electron microscopy (E.M), chromosomes are not visible during
interphase (the non-dividing phase of the cell cycle). Instead, histology dyes are used
to stain DNA, showing a network of very thin threads known as "chromatin."
During prophase, chromatin alters and becomes condensed by folding.
As a result, chromosomes appear as tiny threads.
This well-organized structure emphasizes the many types of spindle microtubules,
their roles within the mitotic apparatus, and the precise alterations that occur
during the prophase of karyokinesis.
For complete and detailed notes on this topic, see below.