Karyokinesis Phases
Karyokinesis involves the division of a cell nucleus during mitosis or meiosis. The two main types of karyokinesis are mitosis and meiosis. The stages of Karyokinesis include:
1. Prophase
Prophase is the initial stage of both mitosis and meiosis. It is the longest phase and is divided into two phases:
- Early prophase
- Late prophase
Early Phase
- It is the first stage of mitosis that follows the S and G2 phases of interphase.
- Chromatin fibers begin to condense into visible chromosomes.
- The mitotic spindle starts forming.
- Centrioles duplicate and move to the opposite poles of the cell.
Late Phase
- It is also known as prometaphase.
- The nuclear envelope breaks down completely.
- The spindle fibers attach at the kinetochores of the tetrads.
- Centrosomes are positioned at opposite poles, establishing the bipolar spindle apparatus.
2. Metaphase
It is the second stage of the mitosis that follows prophase. It is also known as metakinesis.
- Chromosomes align at the cell’s equator, forming the metaphase plate.
- The chromosomes are at their second-most condensed and coiled stage during metaphase.
- Spindle fibers from opposite poles attach to the kinetochore of each chromosome.
- Chromosomes are positioned for equal distribution to daughter cells in the upcoming anaphase.
3. Anaphase
Anaphase is the fourth phase of the mitosis. It is characterised by chromosome s moving towards opposite pole of the cell.
- Kinetochore microtubules shorten.
- Non-kinetochore microtubules lengthen.
- Centrosomes are pushed far apart and the cell elongates as spindle fibers continue to separate chromatids.
- This phase ensure that each daughter cell receives a complete set of chromosomes for genetic stability.
4. Telophase
Telophase is the fifth and last stage of karyokinesis. It is usually followed by cytokinesis, in which the cytoplasm is physically divided to form two daughter cells.
- It starts when the replicated, paired chromosomes have been separated and pulled to opposite sides, or poles, of the cell.
- The decondensation of chromosomes starts.
- The spindle starts disappearing.
- The nuclear envelope assembly around each set of chromosomes.
- Telophase is usually followed by cytokinesis.
Karyokinesis Meiosis
Meiosis consists of two successive cell divisions, known as meiosis I and meiosis II:
Meiosis I
- Prophase I: Chromosomes condense, and homologous chromosomes undergo genetic recombination (crossing over).
- Metaphase I: Homologous chromosomes align at the cell’s equator.
- Anaphase I: Homologous chromosomes separate and move to opposite poles.
- Telophase I: Two haploid cells are formed, each with half the chromosome number of the original cell.
Meiosis II: Similar to mitosis, resulting in the formation of four non-identical haploid daughter cells.
What is Karyokinesis?
Karyokinesis is the process of nuclear division that occurs during cell division mitosis or meiosis, specifically in eukaryotic cells. It is the first step in the M phase of the cell cycle. It is followed by cytokinesis, which is the splitting of the cytoplasm and cell membrane. Karyokinesis is divided into five phases Prophase, Metaphase, Anaphase, Telophase, and Cytokinesis.
The process of karyokinesis allows the growth and expansion of multicellular organisms. It also enables the regeneration of damaged tissues. In this article, we will study Karyokinesis, the stages of karyokinesis, its significance, and the difference between karyokinesis and cytokinesis.
Table of Content
- What is Karyokinesis?
- Stages of Karyokinesis
- Significance of Karyokinesis
- Disturbances of Karyokinesis
- Difference Between Karyokinesis and Cytokinesis
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