Chapter 2

• What are chromosomes made of? How many of them are in a human body cell?

  Chromosomes are made of DNA and there are 46 in a human cell
• Describe the cell cycle


  Before a cell can divide it needs to grow and increase the number of sub-cellular structures (such a ribosomes and mitochondria).

  The DNA then replicates to form two copies of each chromosome.

  In mitosis one set of chromosomes is pulled to each end of the cell and the nucleus divides.

  Finally the cytoplasm and cell membrane divide to form two identical cells
• In what situations is mitosis used in the body?


  Growth, repair and asexual reproduction
• Where does mitosis take place in a plant?


  Mitosis takes place in the meristems of a plant

  
• How do some cells become differentiated to do a certain job?


  Some genes are switched off, meaning that cells will develop different sub-cellular structures for different functions
• What is the difference in terms of differentiation between animal and plant

  cells?

  Many plant cells can differentiate throughout life, whereas most animal cells differentiate at early stages of development
• What are adult stem cells?

  Adults stem cells are undifferentiated cells that can divide to form a few types of cell
• What are embryonic stem cells?

  stem cells from embryos that can differentiate into any specialised cell
• What are some potential uses of stem cells in humans?

  -To make nerve cells to help paralysed people

  -To make pancreas cells to help people with diabetes

  -To make retina cells to help people who are going blind (macular degeneration)

  -To help repair the heart after a heart attack

  -To make whole new organs in the future
• What are some ethical concerns with using embryonic stem cells in medicine?


  The embryo can't give permission, It is wrong to use a potential human being as a source of cells
• What are some risks associated with using embryonic stem cells in medicine?


  May cause cancer, may become contaminated with a virus while in the lab
• What is therapeutic cloning?

  When an embryo is produced with the patient's genes so that stem cells from the embryo can be used as they are a perfect match.
• Name a use of stem cells in plants


  They can be used to make clones of the plant very quickly and cheaply. This is useful for producing lots of rare plants and cloning rare plants that grow well