module 2 (cell division)

• Cell cycle


  1. Interphase (G1, S, G2)

  2. Nuclear division - mitosis or meiosis

  3. Cytokinesis
• Interphase


  Growth and repair (e.g. clonal expansion), DNA replicates and organelles duplicate while cell grows
• Mitosis


  1. Prophase

  2. Metaphase

  3. Anaphase

  4. Telophase

  5. Cytokinesis
• Mitotic index


  Used to determine proportion of cells undergoing mitosis, calculated as a percentage or decimal
• Meiosis


  Two nuclear divisions that result in four genetically different haploid daughter cells
• Haploid


  One copy of each chromosome
• Diploid


  Two copies of each chromosome
• Genetic differences introduced by meiosis

  • Independent assortment of homologous chromosomes, crossing over
• Crossing over


  Occurs between the chromatids of bivalents in prophase I, results in new combinations of alleles in the resulting gamete
• Independent assortment


  Homologous pairs of chromosomes line up opposite each other on either side of the equator during metaphase I, it is random which side of the equator the maternal and paternal pair aligns
• Stem cells


  Undifferentiated cells that can self-renew (continually divide) and become specialised, different types have different differentiation abilities
• Totipotent cells


  Can divide and produce any type of body cell, only occur for a limited time in mammalian embryos
• Pluripotent cells


  Found in embryos and can become almost any type of cell, often used in research
• Multipotent and unipotent stem cells


  Found in mature mammals, can divide to form a limited number of different cell types
• Stem cells could be used in both research and medicine: Repairing damaged tissues, Treatment of neurological conditions such as Alzheimer's and Parkinson's, Research into developmental biology