Cytokinesis is followed by karyokinesis. True or false?
**False.**
**Explanation:**
Cytokinesis and karyokinesis are two distinct processes that occur during cell division. Although they are closely related and often occur simultaneously, cytokinesis is not directly followed by karyokinesis.
**Cytokinesis:**
- Cytokinesis is the process by which the cytoplasm of a cell divides into two daughter cells after the completion of nuclear division (karyokinesis).
- It occurs during the final stages of cell division known as telophase.
- Cytokinesis involves the formation of a contractile ring, composed of actin and myosin filaments, which constricts the cell membrane at the equator of the dividing cell.
- This constriction ultimately leads to the formation of a cleavage furrow, dividing the cytoplasm into two daughter cells.
- Cytokinesis differs in animal and plant cells, with animal cells undergoing constriction and plant cells forming a cell plate.
**Karyokinesis:**
- Karyokinesis refers to the division of the nucleus during cell division.
- It occurs prior to cytokinesis, specifically during the stages of prophase, metaphase, anaphase, and telophase, collectively known as mitosis.
- Karyokinesis involves the replication and segregation of chromosomes into two daughter nuclei.
- During prophase, chromatin condenses into distinct chromosomes, and the nuclear envelope disintegrates.
- In metaphase, the chromosomes align at the equatorial plane of the dividing cell.
- Anaphase is characterized by the separation of sister chromatids, which are pulled towards opposite poles of the cell by spindle fibers.
- Finally, during telophase, the chromosomes decondense, and the nuclear envelope reforms around each set of chromosomes, establishing two distinct nuclei.
In summary, cytokinesis is the division of the cytoplasm, while karyokinesis is the division of the nucleus. They are both essential processes in cell division, but they occur at different stages and are not directly sequential.