Last updated on March 13, 2014 at 10:43 EDT  Ethical dilemmas in
stem-cell research  January 8, 2004  Readers will be well
familiar with the debate on human embryonic stem-cell research.
Whether it is ethical to use such cells for research hinges on
the question of how much respect human embryos deserve. In my
opinion they deserve enough respect to protect them from being
killed in order to harvest stem cells. The potential of stem
cells to alleviate human misery is great, but their potential is
probably realisable through research on adult stem cells, whose
use poses no ethical problems.  The unit of biological life is
the cell. Most of the trillions of our body cells are
differentiated tissue cells, e.g. muscle, liver, kidney, and so
on, each performing functions unique to the tissue to which they
belong. Stem cells, on the other hand, are undifferentiated
cells that can give rise to specialised cells. There are three
main sources of stem cells: a) embryonic stem cells (ES) derived
from five- to seven-day-o