explain the importance of mitosis in the production of genetically identical daughter cells during: growth of multicellular organisms, replacement of damaged or dead cells, repair of tissues by cell replacement, asexual reproduction

Published by Patrick Mutisya · 14 days ago

Cambridge A-Level Biology – Replication and Division of Nuclei and Cells

Replication and Division of Nuclei and Cells

Objective

Explain the importance of mitosis in the production of genetically identical daughter cells during:

  • Growth of multicellular organisms

  • Replacement of damaged or dead cells

  • Repair of tissues by cell replacement

  • Asexual reproduction

Key Concepts

  • Cell cycle – the series of events that a cell undergoes from one division to the next.

  • Mitosis – the division of the nucleus resulting in two genetically identical daughter nuclei.

  • Cytokinesis – the division of the cytoplasm that follows mitosis, producing two separate cells.

  • Genetic identity is essential for maintaining tissue function and organismal integrity.

The Mitosis Cycle

Mitosis is divided into distinct phases, each characterised by specific chromosomal events.

  1. Prophase: Chromatin condenses into visible chromosomes; the mitotic spindle begins to form.

  2. Prometaphase: Nuclear envelope breaks down; spindle fibres attach to kinetochores.

  3. Metaphase: Chromosomes align at the metaphase plate.

  4. Anaphase: Sister chromatids separate and are pulled toward opposite poles.

  5. Telophase: Chromatids reach the poles; nuclear envelopes re‑form around each set of chromosomes.

  6. Cytokinesis: Cytoplasmic division creates two separate daughter cells.

Why Genetically Identical Cells Are Required

For most somatic tissues, the function of each cell depends on a specific set of genes being expressed in the same way as its neighbours. Identical DNA ensures that:

  • Enzymatic pathways are conserved across the tissue.

  • Structural proteins (e.g., collagen in connective tissue) are produced uniformly.

  • Cell‑cell communication signals remain consistent.

  • Developmental patterns are maintained during growth.

Roles of Mitosis in Organisms

RoleDescriptionTypical Example
Growth of multicellular organismsIncreasing cell number to enlarge tissues and organs while preserving genetic identity.Embryonic development of a human fetus.
Replacement of damaged or dead cellsContinuous turnover of cells that have limited lifespans.Renewal of epidermal skin cells.
Repair of tissuesRapid proliferation of cells at a wound site to restore tissue integrity.Healing of a cut on the liver.
Asexual reproductionGeneration of a new organism from a single parent without genetic recombination.Vegetative propagation in strawberry plants (runners).

Illustrative Examples

  • Growth: During childhood, the length of long bones increases because chondrocytes in the growth plate undergo mitosis, adding new cells to the bone matrix.

  • Replacement: Red blood cells have a lifespan of \overline{120} days; the bone marrow continuously produces new erythrocytes via mitosis.

  • Repair: After a liver laceration, hepatocytes at the wound edge re‑enter the cell cycle, divide, and replace lost tissue.

  • Asexual reproduction: In many algae, a single cell can undergo repeated mitotic divisions to form a multicellular colony that is genetically identical to the parent.

Suggested diagram: Stages of mitosis showing chromosome condensation, alignment, separation, and formation of two daughter nuclei.

Summary

Mitosis is the fundamental mechanism by which multicellular organisms increase cell number, maintain tissue integrity, and reproduce asexually while preserving the genetic blueprint of the parent cell. Understanding the precise control of this process is essential for appreciating normal development, tissue homeostasis, and the consequences when mitotic regulation fails (e.g., cancer).