Stem cells are unique from other types of cells in two
major ways. Firstly, they are unspecialized cells that
___1___ themselves
for extended periods of time through cell division.
Secondly, under certain physiological or experimental
conditions, stem cells can be ___2___
to become cells with special functions. Scientists ___3___
work with two kinds of stem cells from animals and
humans. These are the embryonic stem cells and adult
stem cells, which have different functions and
characteristics. Scientists firs discovered ways to
obtain or derive stem cells from early mouse embryos
more than 20 years ago. In 1998, after many years of
thorough study on the biology of mouse stem cells, the
discovery was made on how to isolate stem cells from
human embryos and grow the cells in the laboratory.
these cells are identified as human embryonic stem
cells.
Scientist hypothesize that stem cells may in the ___4___
become the basis for treating diseases such as
Parkinson's disease, diabetes, and heart disease.
Scientists want to study stem cells in the laboratory so
they can learn about their indispensable properties and
___5___ what makes
them different from other cell types. |