Cell Divison

• What are chromosomes made of?

  DNA molecules
• What is a gene?

  A section of DNA which codes for a specific protein.
• How many chromosomes are found in normal cells?

  46
• How many chromosomes are found in gametes?

  23
• What are the three main stages of the cell cycle.

  -Replication of DNA and synthesis of organelles

  -Mitosis

  -Divison of cells
• Why is mitosis important?

  Produces identical daughter cells and is used for growth, repair, replacement and asexual reproduction
• Describe the first stage of the cell cycle?

  Longest Stage - Cells grow and increase in mass, replicate DNA and synthesise more organelles
• Describe the second stage of the cell cycle.

  Each chromosome in a pair is pulled to opposite poles of the cell, then the nucleus divides.
• Describe the third stage of the cell cycle?

  The cytoplasm and cell membrane divide - two identical daughter cells are produced.
• What is a stem cell?

  An unspecialised cell which is capable of differentation.
• What is the function of stem cells in embryos?

  Embryonic stem cells can differentiate into many different types of cells.

  Embryonic stem cells may be able to treat many conditions such as paralysis and diabetes by dividing to replace damaged cells.
• What is the function of stem cells in bone marrow?

  Adult stem cells can differentate into some several types of cells to replace dead or damaged tissues. For example, bone marrow stem cells can form many types of blood cell.
• Where are stem cells found in plants?

  Meristems
• What is the function of stem cells in meristems?

  Meristem cells maintain the ability to differentiate into any type of plant cell throughout their lifespan - they can differentiate into any specific cell needed for the plant.
• What is therapeutic cloning?


  A cloning method where an embryo is produced with the same genetic makeup as the paitent. The stem cells which originate from the embryo will not be rejected by the paitent's immune system, so can be used to treat certain medical conditions.
• What are the advantages of cloning plants using meristem stem cells?

  Can prevent rare plants from becoming extinct.

  Can produce large numbers of plants with a favourable characteristics.

  Can produce identical plants for research.
• What are issues associated the use of stem cells?

  Many embryonic stem cells are sourced from aborted embryos - some people have religious and ethical concerns.

  Development of stem cells is slow and expensive

  Adult stem cells with viruses could transfer infections to paitents.

  If donor stem cells do not have similar genetic make up to the paitent an immune response will be triggered.