Biology

• What happens during the third stage of the cell cycle?

  the cytoplasm and cell membrane divide, forming two identical daughter cells
• What happens during mitosis?


  One set of chromosomes is pulled to each end of the cell and the nucleus divides
• What happens during the first stage of the cell cycle?

  Cells grow bigger; chromosomes duplicate; number of sub-cellular structures (e.g. ribosomes and mitochondria) increases
• What is the purpose of mitosis

  cell regeneration, growth, repair, and asexual reproduction
• What is cell division by mitosis?

  body cells divide to form two identical daughter cells
• What is the cell cycle?


  Replication (longest) Mitosis Division
• Give one disadvantage of using plant meristems to clone plants

  no genetic variation, so, for example, an entire cloned crop could be destroyed by a disease
• Give two advantages of using plant meristems to clone plants

  • rare species can be cloned to protect them from extinction• plants with special features (e.g., disease resistance) can be cloned to produce many copies
• What are plant meristems?


  area where rapid cell division occurs in the tips of roots and shoots
• Disadvantages of using embryonic stem cells

  *the body might reject the cell when used as treatment*could form a tumor*ethical concerns: a common way to get involves destruction of the embryo
• Advantages of embryonic stem cells

  No consent required, obtainable via embryos discarded in IVF, can be used to make any type of cell, less risk of rejection if used via therapeutic cloning
• Disadvantages of using adult stem cells

  *hard to isolate and grow*few in number*may have more abnormalities than embryonic cell*Only differentiates into certain stem cells
• Advantages of using adult stem cells

  can be directly taken from the patient so this avoids ethical issues; lowers risk of transplant rejectionReliable
• Give one advantage of using therapeutic cloning

  stem cells from the embryo are not rejected when transplanted because they have the same genes as the patient
• What is therapeutic cloning?

  patient's cells are used to create an early embryo clone of themselves - stem cells from the embryo can then be used to treat the patient's medical conditions
• Where are embryonic stem cells found?

  early human embryos (usually from spare embryos from fertility clinics)
• What are embryonic stem cells?

  stem cells from embryos that can differentiate into any specialised cell
• Where can adult stem cells be found?

  bone marrow
• What are adult stem cells?

  stem cells from adults that can only differentiate into certain specialised cells
• What is a stem cell?

  undifferentiated cell that can differentiate into one or more specialised cell types
• Mitosis is the process by which cells divide to produce two genetically identical daughter cells.