Question

How is a cell formed?

Answer 1

Cells:

1. Cells take birth from the preexisting cells through the process of mitosis.
2. Through the cell cycle, new cells are created from the already existing cells.
3. One cell is capable of replicating, making a copy of self leading to the formation of new daughter cells.
4. For every cell cycle to take place, one of the first tasks is to make an exact copy of its DNA.

Phases of the Cell Cycle

Mitosis

1. Mitosis occur in the diploid somatic cells of animals, haploid male and drone of honey bees.
2. Mitosis is responsible for genetics and growth for the repair of multicellular organisms
3. In humans, the epithelial lining, lining of the gut, and blood cells are replaced continuously
4. In plants, tissues divide continuously throughout their life
5. Mitosis accounts for the asexual reproduction or vegetative propagation, where identical individuals are formed
6. Karyokinesis occurs in four sequential stages:
   1. Prophase
   2. Metaphase
   3. Anaphase
   4. Telophase
7. Karyokinesis is followed by cytokinesis

• Prophase
  1. Chromosomes untangle and compressed
  2. Two chromatids attached to the centromere
  3. Each centrosome radiates microtubules (asters)
  4. Mitotic apparatus constitute spindle fibers and asters
  5. Golgi bodies, nucleolus, endoplasmic reticulum, and nuclear membrane disappear
• Metaphase
  1. Complete disintegration of the nuclear envelope
  2. Two sister chromatids attached by the centromere aligned at the equator, i.e. metaphase plate
  3. Each chromatid is attached to spindle fibers from opposite poles at kinetochores
• Anaphase
  1. Splitting of centromere and two sister chromatids separate and go towards the opposite poles
  2. Sister chromatids become the daughter chromosome.
• Telophase:
  1. Chromosome cluster at opposite pole and decondense
  2. A nuclear envelope develops around each cluster of chromosomes and two daughter nuclei are formed
  3. The nucleolus, endoplasmic reticulum, and Golgi apparatus are reformed