Cell division

• Cancer cells originate from healthy cells where the cell cycle is not being controlled normally. This can lead to uncontrolled cell division and the formation of tumours.
• Drugs used to destroy cancer cells also cause damage to healthy cells, although are more effective against the cancer cells.
• A high dose of chemotherapy is given


  To prepare the patient for a stem cell transplant
• Stem cells are introduced into the patient


  Careful monitoring of the patient is required after the procedure
• Careful monitoring of the patient is required after a stem cell transplant procedure due to potential issues associated with the transplant
• Embryonic stem cells have the property that they can give rise to all the different types of cells in a multicellular organism
• Interphase


  The period of time that immediately precedes the visible stages of mitosis
• The mass of DNA in an unfertilised egg cell is the same as the mass of DNA in a sperm cell of the same species
• Cell division in tissues such as muscle tissues


  Allows growth and repair of the tissue
• Events that occur during prophase of mitosis


  • Chromosomes condense
  • Nuclear envelope breaks down
• Diploid


  A cell that contains two complete sets of chromosomes
• Events that take place in interphase of the cell cycle


  • Cell growth
  • DNA replication
  • Preparation for cell division
• Amount of DNA in each cell at different stages of the cell cycle


  • Interphase (start): 10 units
  • Metaphase: 20 units
  • Interphase (end): 10 units
  • End of sperm production (one sperm cell): 5 units
• The process of mitosis was first termed 'cell division' rather than 'cell multiplication' because the number of cells increases, even though the cells are dividing
• Stages of mitosis in correct order


  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
• Interphase


  Cell growth, DNA replication, and preparation for cell division
• The root tip is used to study mitosis because it contains rapidly dividing cells
• Using a microscope to obtain a clear image of cells in the root tip squash


  1. Adjust focus

  2. Adjust illumination

  3. Adjust magnification
• Staining


  Can be added to the root tip squash to make the chromosomes visible
• The stage of mitosis shown in Figure 1 is prophase
• What is happening in Figure 1 (prophase of mitosis)


  • Chromosomes are condensing
  • Nuclear envelope is breaking down
  • Spindle fibres are forming
• The stages of mitosis include interphase, prophase, metaphase, anaphase, telophase, and cytokinesis.
• Meiosis is the process by which sex cells (gametes) are produced, resulting in four haploid daughter cells with half the number of chromosomes as the parent cell.
• Mitosis is the process by which cells divide to produce two genetically identical daughter cells.
• Interphase is when the cell grows and replicates its DNA.
• Prophase is where the nuclear membrane breaks down, spindles form, and chromatin coils into chromosomes.
• Metaphase is where the chromosomes line up at the equator of the cell.
• Chromatin

  A structure composed of DNA wrapped around histone proteins, present in the nucleus throughout the cell cycle. It is less condensed and more diffuse than chromosomes.
• Chromosomes

  Structures that contain the genetic material of a cell, formed from condensed chromatin. They are visible under a microscope during cell division and are made up of two sister chromatids held together at the centromere.
• Cell division (mitosis and meiosis)

  A process in which a cell divides to produce two identical daughter cells. This involves the condensation of chromatin into chromosomes, the separation of the chromosomes, and the formation of two separate nuclei.
• Chromatin condensation

  The process by which chromatin becomes more compact and condensed during cell division. This allows the chromosomes to be easily seen and separated during cell division.
• Nuclear envelope breakdown

  The disintegration of the nuclear envelope, which surrounds the chromatin in the nucleus, during cell division. This allows the chromosomes to move freely within the cell.
• Chromosome separation

  The process by which the chromosomes are pulled apart by the spindle fibers and separated into two identical sets during cell division.
• Interphase (start)

  10 units of DNA
• Interphase (end)

  10 units of DNA
• Metaphase

  20 units of DNA
• End of sperm production (one sperm cell)

  5 units of DNA