Division and Differentiation

• Cancer cell


  Grows and divides in an uncontrolled way to produce a tumour
• Differentiation


  Changes to cells which specialise them for different functions
• Diploid


  A cell that has two sets of chromosomes
• Embryonic stem cells


  Stem cells from embryos that can divide to become any type of cell
• Ethical issue


  Issue affecting human attitudes and decisions in relation to making certain choices
• Germline cell


  A diploid cell that can divide by meiosis to give rise to gametes; can also divide by mitosis to produce more germline cells
• Haploid


  A cell that has one set of chromosomes (e.g. gametes)
• Lymphocyte


  Type of white blood cell involved in the specific immune response
• Meiosis


  Type of cell division which produces 4 haploid gametes from germline cells
• Mitosis


  Division of the nucleus of somatic or germline cells to produce two identical daughter cells
• Multipotent stem cell


  Stem cell that has the potential to make almost all cell types found within a particular tissue
• Phagocyte


  White blood cell that can engulf and destroy foreign material
• Pluripotent stem cell


  Stem cell that has the potential to make almost all differentiated cell types of the body
• Somatic cell


  Body cell that divides by mitosis to form more body cells
• Therapeutic


  Used as part of a medical therapy
• Tissue stem cells


  Stem cells from tissue that divide and differentiate to become cells of that tissue
• Tumour


  Mass of cancer cells produced by excessive, uncontrolled cell division
• Multicellular organisms have cells organised into groups of cells called tissues, which are formed from specialised cells that carry out a particular function
• Tissues themselves become grouped together to form organs: Most organs are also specialised for certain functions
• The final level of organisation is the organ system
• Levels of organisation


  • Cells
  • Tissues
  • Organs
  • Systems
• Somatic cell


  Any cells in the body other than cells involved in reproduction divide by mitosis to form more somatic cells
• Germline cell


  Gametes (sperm and ova) and the stem cells that divide to form gametes divide by meiosis
• The nucleus of all human somatic cells contains a complement of 46 chromosomes - known as the diploid number and denoted by the symbol 2n
• Each chromosome has a matching or homologous partner (identical in size and appearance) present in the other haploid set
• Somatic stem cells divide by mitosis to form more somatic cells each of which has the diploid chromosome number
• Germline cells can divide by mitosis and by meiosis
• Meiosis


  1. First division separates homologous chromosomes

  2. Second division separates chromatids
• In sexual reproduction, two gametes unite to form the zygote of the new individual
• The resulting zygote has just one, complete set of chromosomes (diploid)
• Zygote development


  1. Zygote (2n)

  2. Mitosis

  3. Adult (2n)

  4. Meiosis

  5. Gametes (n)
• The sperm cell (haploid) and egg cell (haploid) of parents provide the chromosomes in somatic cells
• Mitosis replicates cells of somatic cells
• Mitosis


  A type of cell division that produces somatic (body) cells allowing for growth and/or repair of a multicellular organism and also promotes reproduction of unicellular organisms
• Mitosis occurs in all body tissues
• Mitosis produces identical cells with the same number of chromosomes as the original cell
• Germline stem cells divide by mitosis and by meiosis
• Division by mitosis produces more germline stem cells
• All the somatic cells in an organism are produced as a result of mitosis of a zygote
• All cells are initially genetically identical, but change to become structurally and functionally different from each other