Karyokinesis, Definition, Types, Process Function and Differences

Karyokinesis is the process of dividing the nucleus that takes place during the M phase of the cell cycle. As the initial step in this phase, karyokinesis occurs separately from cytokinesis. This process is crucial because it guarantees the equal distribution of genetic material, resulting in the separation of daughter chromosomes into two daughter nuclei.

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Karyokinesis Definition

Karyokinesis Phases

Prophase

• Chromosomes condense, becoming visible as compact mitotic chromosomes, each consisting of two chromatids joined at the centromere.
• Centrosomes move to opposite poles of the cell, radiating microtubules called asters, forming the mitotic apparatus.
• By the conclusion of prophase, the golgi complex, endoplasmic reticulum (ER) , nucleolus, and nuclear envelope become invisible when viewed under the microscope.

Metaphase

• Chromosomes arrange themselves along the equatorial plane of the cell, termed the metaphase plate.
• Spindle fibers attach to the kinetochores (disc-shaped structures) on the centromeres of each chromosome.
• One chromatid of each chromosome is attached to spindle fibers from one pole, and the sister chromatid is attached to spindle fibers from the opposite pole.

Anaphase

• Centromeres split, and chromatids separate, becoming individual daughter chromosomes.
• Chromosomes are pulled towards opposite poles, with the centromeres leading and the arms trailing behind.

Telophase

• Chromosomes cluster at opposite poles and decondense, losing their distinct identity.
• Nuclear envelopes form around the chromosomal clusters, creating two daughter nuclei.
• The nucleolus, golgi complex, and endoplasmic reticulum reform.

Importance of Karyokinesis

• Ensuring accurate distribution of chromosomes and genetic material to daughter cells during cell division.
• Maintaining genetic stability by preserving species-specific information encoded in DNA .
• Supporting essential processes like growth, tissue repair, and maintaining the overall structure of the organism.
• Facilitating cell regeneration, which is vital for the survival of living organisms.
• Enabling cells and tissues to mature, develop, and renew within a set period, ensuring healthy organismal function.

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MCQs of Karyokinesis

Q1. Find the correct sequence of karyokinesis.

1. Metaphase ,prophase ,telophase ,prophase
2. Prophase, metaphase, anaphase, telophase
3. Anaphase, prophase, telophase, metaphase
4. Telophase, metaphase, anaphase, prophase `

Q2. Cells at the end of prophase, when viewed under the microscope, do not show:-

1. Golgi body and ER
2. Nucleolus
3. Nuclear envelope
4. All of these

Q3. The morphology of chromosomes can be best studied at:

1. Prophase
2. Metaphase
3. Anaphase
4. Telophase

Answers of MCQs of Karyokinesis