B2

• What does the nucleus contain?

  Chromosomes made of DNA
• What are chromosomes made of?

  DNA
• What happens during the cell cycle?

  The genetic material is doubled then divided into two identical cells
• How many stages are there of the cell cycle

  3
• What happens to a cell in stage 1 before it divides

  Grow and increase number of sub cellular structures, the DNA replicates to make two copies of each chromosome
• What happens to the nucleus during mitosis


  Sets of chromosomes move apart and the nucleus or cell membrane divides
• What happens in stage 3 of the cell cycle after mitosis


  The cytoplasm and cell membrane divide to make two identical cells
• Why is cell division by mitosis important

  Needed for growth and development of multicellular organisms
• What is a stem cell

  An undifferentiated cell which is able to differentiate and divide to form lots of cells of the same type
• What are meristems


  Plant stem cells that can differentiate into any type of plant cell throughout the life of the plant
• What can plant stem cells be used for

  They can be used to make clones of plants quickly and economically
• What are the disadvantages of embryonic stem cells

  Cause death to the embryo, unreliable, unethical
• What are the advantages of embryonic stem cells

  Low chance of rejection, painless, divides quickly (every 30 minutes)
• What are the advantages of adult stem cells


  Permission can be given to collect stem cells and they are safe
• What are the disadvantages of adult stem cells

  Risk of infection from operation

  Painful to donate
• Why do some scientists have concerns about the use of stem cells


  Could cause cancer
• What are the sources of adult stem cells

  Bone marrow

  Umbilical cord

  Blood

  Skin
• Why might stem cells from embryos be more useful than adult stem cells

  They can become more types of cells

  Wider range for differentiation
• What happens during the process of therapeutic cloning

  An embryo is produced with the same genes as the patient
• What are the advantages of therapeutic cloning

  May cure diseases

  Produce replacement cells

  Treat diabetes and paralysis

  Cells unlikely to be rejected

  Cells and tissues of any type can be made

  Reduces waiting time for transplants
• What are the disadvantages of therapeutic cloning

  Potential life is killed (unethical)

  Shortage of egg donors

  May transfer viral infection

  Poor success rate
• Why do most organisms have an even number of chromosomes in their body cells

  Chromosomes come in pairs