Cell Division

Basics of Cell Division

  • Cell division is a fundamental process in organisms where a single cell divides into two or more distinct cells.
  • The two forms of cell division are mitosis and meiosis.
  • Mitosis is used for the growth and repair of tissues and occurs in body cells, resulting in two identical daughter cells.
  • Meiosis occurs in sex cells, or germ cells, and produces four genetically unique cells.

The Process of Mitosis

  • Mitosis has four major stages: prophase, metaphase, anaphase, and telophase.
  • In prophase, chromatids condense and the nuclear envelop starts to disappear.
  • During metaphase, the chromatids line up along the centre of the cell.
  • In anaphase, the chromatids separate and move towards opposite poles.
  • Finally, during telophase, a nuclear envelope forms around each set of chromatids at the opposite ends of the cell, which then divide to produce two new cells.

The Process of Meiosis

  • Meiosis involves two rounds of cell division - meiosis I and meiosis II, each with the steps similar to those in mitosis.
  • In the first division, the homologous pairs of chromosomes are separated resulting in two cells, each with a haploid set of chromosomes.
  • The second division separates the sister chromatids within each haploid cell, resulting in four genetically diverse gametes.

Role of Cell Division

  • Cell division is critical for growth, repair, and reproduction in organisms.
  • In multicellular organisms, cell division enables the organism to grow and replace cells that have been damaged or lost.
  • In single-celled organisms, cell division is a form of reproduction, known as asexual reproduction.

Cell Division and Genetic Variability

  • Cell division plays an important role in genetic variability.
  • During meiosis, crossing over and independent assortment create new combinations of genes, which lead to unique traits in offspring.
  • Mitosis, on the other hand, creates identical cells which facilitate growth and repair.
  • Errors during cell division can result in genetic disorders and illnesses, such as cancer.
  • Mutations can occur if cells don’t divide correctly, or if DNA replicates incorrectly.
  • The most common type of genetic disorder due to an error in cell division is Down Syndrome, where an individual has an extra copy of chromosome 21.