1.1

• Somatic cells


  Any cell in the body except from cells involved in reproduction
• Mitosis


  A type of cell division which produces daughter cells identical to the parent
• Daughter cells


  Cells formed from the division of a cell
• Germline cells


  Gametes (sperm and ova) and the stem cells that divide to form gametes
• Meiosis


  Special type of division which reduces the chromosome number by half from diploid to haploid
• Gamete


  Sex cell (sperm in males; ova in females)
• Diploid


  A cell that contains two sets of chromosomes (46)
• Haploid


  A cell that contains one set of chromosomes (23)
• Zygote


  A fertilised egg cell
• Cellular differentiation


  The process by which a cell expresses certain genes to produce proteins characteristic for that type of cell, allowing it to carry out specialised functions
• Stem cells


  Unspecialised cells that have the potential to differentiate into a wide range of cells
• Adult tissue stem cells

  Stem cells found in specific locations in an adult and can only differentiate into a limited number of related cell types
• Embryonic stem cells


  Stem cells found in early embryos and can differentiate into almost any cell types
• Ethical


  Relating to right or wrong
• In-vitro fertilisation (IVF)


  When an embryo is created outside the human body in a laboratory using an egg cell and sperm cell
• Cancer


  A disease caused by uncontrolled cell division of normal cells causing the formation of a tumour
• Tumour


  The lump of cells formed as a result of uncontrolled cell division
• Carcinogen


  A chemical or other agent which causes cancer
• Mutation


  A random or spontaneous change in the structure of DNA
• Ultraviolet radiation


  Radiation associated with sunburn and skin cancer
• Mitosis


  1. DNA replicates

  2. Chromosomes line up across the centre of the cell

  3. One set of chromosomes is pulled to each end of the cell

  4. Cytoplasm and cell membranes divide for two identical cells
• Mitosis vs Meiosis


  • Mitosis produces 2 daughter cells with full set of chromosomes (diploid)
  • Meiosis produces 4 daughter cells with half set of chromosomes (haploid)
  • Mitosis produces genetically identical daughter cells
  • Meiosis produces genetically different daughter cells
• Meiosis


  1. Copies of genetic information (chromosomes) are made

  2. Cell undergoes two divisions, first separating homologous chromosomes, then separating chromatids

  3. Produces four gametes, each with a single set of chromosomes (haploid)

  4. Gametes are genetically different due to chromosome separation and reshuffling
• Cellular differentiation


  Cells express specific genes to produce specific proteins characteristic of a certain cell type, allowing specialisation
• Embryonic stem cells


  Cells in the very early embryo that can differentiate into any cell type, being pluripotent
• Adult tissue stem cells

  Involved in growth, repair and renewal of cells in a particular tissue, being multipotent
• Therapeutic and research uses of stem cells

  • Therapeutic: Repair of damaged/diseased organs or tissues
  • Research: Model cells to study disease development and drug testing
• Stem cells from the embryo can self-renew under the right conditions in the lab, providing information on cell processes
• Unused embryos from IVF are a source of embryonic stem cells
• Use of embryonic stem cells can offer effective treatment but involves destruction of embryos
• There are ethical concerns around when an embryo should be considered a person
• Cancer cells


  Divide excessively as they do not respond to regulatory signals, forming a tumour
• Benign tumours


  Grow slowly and do not invade other parts of the body
• Malignant tumours


  Grow quickly, invade neighbouring tissues and spread through the body
• Causes of cancer


  • Genetic factors
  • Carcinogens (causing mutations)
  • Smoking
  • Alcohol intake
  • Viruses
  • Exposure to ultraviolet radiation