Producing new cells

• Mitosis is a type of cell division that results in two daughter cells each identical to the parent cell.
• Haploid is a cell which has single set of chromosomes

  Diploid is a cell with two matching sets of chromosomes
• Chromosomes are thread like structures found inside the nucleus of a cell
• There are three reasons why cells need to divide

  1. growth
  2. repair of damaged tissues and replacement of dead cells
  3. reproduction in unicellular organisms
• Events of mitosis

  1. DNA replicates and the chromatids join together at the centromere forming double stranded chromosomes
  2. the nuclear membrane breaks down and the chromosome shorten and thicken so they are visible under the microscope
  3. double stranded chromosomes line up along the equator
  4. spindle fibres attach to the double stranded chromosomes
  5. spindle fibres shorten and the chromosomes are pulled to opposite poles and are now single stranded
  6. two new nuclei are formed and the cytoplasm begins to pinch
  7. the cytoplasm divides to produce two new identical cells
• The importance of mitosis

  • maintains the diploid chromosome complement of the new cells, providing the body with new cells that can be used for growth and repair
  • prevents the loss of genetic information and ensure the daughter cells carries out the exact same functions as the original parent cell
• Stem cells are unspecialised cells found in animals.They have the potential to become various body cells and are used in growth and repair

  They can divide to produce either

  • more stem cells by mitosis
  • cells that develop into specialised cells- a cell that has become differentiated to perform a specific function
• Two examples of stem cells

  1. embryonic stem cells
  2. adult stem cells
• Embryonic stem cells

  • found in embryos
  • can divide to become almost any type of cell in the body
• Adult stem cells

  • found in tissues and organs of the body
  • have more limitations than embryonic stem cells
  • only able to form cells from the tissue or organ they come from
• Multicellular organism is an organism that has more than one cell. They are made up of tissues and organs
• Hierarchy of organ systems

  cells -----> tissues -----> organs -----> organ system

  • a tissues is a group of cells
  • an organ is a group of tissues
  • an organ system is a group of organs

  An organ contains cells which are specialised for a particular function and a group of organs work together to form systems