B1.2 - Cell Division

• How is DNA found in the body?

  The nucleus of a cell contains 46 (23 pairs) chromosomes made of DNA molecules. Each chromosome carries a large number of genes. In body cells the chromosomes are normally found in pairs
• Interphase:

  • The cell spends most of its life in this phase
  • DNA in chromosomes copies itself ready for mitosis
• Prophase:

  • DNA in chromosomes and their copies condenses to become more visible
  • The membrane around the nucleus disappears
• Metaphase:

  • Chromosomes and their copies line up in the middle of the cell
• Anaphase:

  • Chromosomes and their copies are pulled to different ends of the cell
• Telophase:

  • New membranes form around the chromosomes at each end of the cell
• Cytokinesis:

  • The cell membrane pinches in and eventually divides into two daughter cells
• What are the names of the different stages of Mitosis?

  Interphase, prophase, metaphase, anaphase, telophase and cytokinesis
• What is Mitosis important for?

  The growth and development of multicellular organisms.
• When does mitosis occur and for what reason?

  Mitosis is needed for repair and replacement of cells: at site of wound or injury, during growth spurts, and during production of red blood cells in bone marrow (which happens all the time).
• What is a stem cell?

  A stem cell is an undifferentiated cell of an organism which is capable of dividing (giving rise) to many more cells of the same type (undifferentiated stem cells). From these cells, other cells can arise through the process of differentiation.
• Cloning of stem cells

  Stem cells from human embryos and adult bone marrow can be cloned and made to differentiate into many different types of human cells.
• Conditions from which people may benefit from extra cloned stem cells.

   Spinal cord injuries, type 1 diabetes, Parkinson's disease, amyotrophic lateral sclerosis, Alzheimer's disease, heart disease, stroke, burns, cancer and osteoarthritis.
• Ethical and religious arguments against stem cell use in embryos

  No consent from the embryo, Killing the embryo which is a potential human life, religious beliefs
• Advantages and Disadvantages of stem cell research

  A - Treats conditions, embryos can become any cell

  D - Rejection of cells, limited supply, virus transmission
• Advantages and disadvantages of using embryos to gain stem cells

  A - Can develop into most types of cell, each divides every 30 minute, low chance of the immune system rejecting the cells.

  D - Costs $5000 to collect a few cells, ethical issues, more research is needed.
• Advantages and disadvantages of using adult bone marrow for stem cells

  A - Costs $1000 to collect a few cells, adults can give consent, considered to be a safe procedure

  D - Can only develop into a few types of cell, each divides every 4 hours, high chance of the immune system rejecting the cells.
• Uses of cloning in plants using meristem

  Producing new plants by cloning is quicker than allowing plants to reproduce and collecting and sowing seeds. It’s therefore an effective way of producing new individuals from rare and endangered plants, helping to preserve the species. Clones will be genetically identical to the original plant providing the meristem cells. This is useful to provide crop plants for large-scale cultivation that have desirable characteristics such as disease resistance. Tissue culture and cloning are important in growing identical plants produced by genetic engineering.
• Can cloning occur in plants?

  Yes. Stem cells from meristems in plants can be used to produce clones of plants quickly and economically.