Mitosis & Cell Cycle Summary

Mitosis and Cell Cycle Notes

Mitosis Overview

  • Mitosis: Division of the nucleus to form somatic cells.
  • Produces daughter cells that are genetically identical to the parent cell.
  • Key for growth and tissue repair in multicellular organisms.

Meiosis Overview

  • Meiosis: Division of the nucleus to form sex cells (gametes).
  • Produces cells with half the number of chromosomes.
  • Involves gametogenesis, resulting in genetic diversity for sexually reproducing organisms.

Cell Cycle

  • Definition: Interval between one cell division and the next.
  • Composed of:**
    • Interphase (>90% of the cycle): Cell prepares for division, synthesizes RNA and proteins, replicates DNA.
    • Mitosis (5-10%): Actual division of the cell's nuclear contents.

Chromosome Structure

  • Chromatin: DNA and protein complex; condenses to form visible chromosomes during mitosis.
  • Human Karyotype: 46 chromosomes in somatic cells.
  • Centromere: Links pairs of sister chromatids and anchors kinetochores for spindle attachment.

Phases of Mitosis

  1. Prophase: Chromatin condenses, nuclear membrane breaks down, spindle apparatus forms.
  2. Metaphase: Chromosomes align along the metaphase plate.
  3. Anaphase: Sister chromatids separate and move to opposite poles.
  4. Telophase: Nuclear membranes form around daughter nuclei, chromosomes de-condense.

Cytokinesis

  • Division of the cytoplasm, forming two distinct daughter cells.
  • Cleavage furrow forms and deepens to separate the cells.
  • Actin and myosin interact to complete the division.

Mitosis in Development

  • Rapid cell division during embryonic development; slows as organism matures.
  • Different cell types have varying division rates to replace cells (e.g., 1-2% of human cells are replaced daily).

Apoptosis

  • Programmed cell death; helps maintain healthy tissue and development by removing damaged cells.

Key Differences: Mitosis vs Meiosis

  • Mitosis: Produces identical diploid cells for growth and repair.
  • Meiosis: Produces unique haploid gametes for sexual reproduction.