Cell Division

• What are chromosomes made up of?

  DNA molecules combined with proteins
• What do chromosomes contain?

  Genes which provide instructions for protein synthesis
• How many chromosomes are found in human body cells?

  46
• How many chromosomes are found in gametes?

  23
• How are chromosomes arranged in the nucleus of a body cell?

  Arranged in pairs forming 23 pairs
• What are the three main stages of the cell cycle?

  1. Replication of DNA and synthesis of organelles
  2. Mitosis
  3. Division of cell
• Why is mitosis important?

  Produces identical cells with the same genetic information
• What happens during the first stage of the cell cycle?

  Cells grow, replicate DNA, and synthesize organelles
• What occurs during the second stage of the cell cycle?

  Chromosomes are pulled to opposite poles and the nucleus divides
• What happens during the third stage of the cell cycle?

  The cytoplasm and cell membrane divide, producing two identical daughter cells
• What is a stem cell?

  An unspecialised cell capable of differentiation
• What is the function of stem cells in embryos?

  Can replicate and differentiate into many cell types
• What is the function of stem cells in adult bone marrow?

  Can differentiate into several cell types to replace tissues
• What is the function of stem cells in plant meristems?

  Can differentiate into any type of plant cell
• What is therapeutic cloning?

  A method to produce embryos with the same genetic makeup as the patient
• What are the advantages of cloning plants using meristem stem cells?

  • Prevent rare plants from becoming extinct
  • Produce large numbers of plants with favorable characteristics
  • Create identical plants for research
• What are issues associated with the use of embryonic stem cells?

  • Ethical objections due to sourcing from aborted embryos
  • Slow, expensive, and difficult development of therapies
  • Risk of infections from adult stem cells
  • Immune response if donor cells differ genetically