1.2-cell division

• What are chromosomes made up of?

  DNA molecules combined with proteins
• What do chromosomes contain that is essential for protein synthesis?

  Genes which provide instructions
• How many chromosomes are found in the nucleus of human body cells?

  46
• What is a gene?

  A section of DNA which codes for a protein
• How many chromosomes are found in the nucleus of gametes?

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

  Arranged in pairs forming 23 pairs
• Why is mitosis important?

  Produces identical cells for growth and repair
• What are the three main stages of the cell cycle?

  1. Replication of DNA and synthesis of organelles
  2. Mitosis
  3. Division of cell
• Describe the first stage of the cell cycle.

  Cells grow, replicate DNA, and synthesize organelles
• Describe the second stage of the cell cycle.

  Chromosomes are pulled to opposite poles, nucleus divides
• What is a stem cell?

  An unspecialised cell capable of differentiation
• Describe the third stage of the cell cycle.

  Cytoplasm and cell membrane divide, producing daughter cells
• What is the function of stem cells in embryos?

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

  Differentiate to replace dead or damaged tissues
• What is therapeutic cloning?

  A method to produce embryos with the same genetic makeup
• What is the function of stem cells in plant meristems?

  Differentiate into any type of plant cell
• What are the advantages of cloning plants using meristem stem cells?

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

  • Ethical objections to sourcing embryonic stem cells
  • Slow, expensive, and difficult development of therapies
  • Risk of infection from adult stem cells
  • Immune response from genetically dissimilar donor cells