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Therapeutic Cloning
The production of human embryos for use in research is known as therapeutic cloning.
This type of cloning, also called embryo cloning, is designed to harvest stem cells
that can be used to study human development and to treat disease. The purpose is not
to create cloned human beings. Stem cells are of great value to biomedical researchers
due to their ability to generate virtually any type of specialized cell in the human body.
These cells are extracted from the egg after it has divided for five days. At this stage
of development, the egg is called a blastocyst. In extracting the egg, the embryo is
destroyed; this raises a variety of ethical concerns. Researchers in the stem cell are
hoping that one day these cells can be used as replacement cells to treat Alzheimer's,
cancer, and other diseases.
Scientists from Advanced Cell Technologies (ACT), a biotechnology company located in
Massachusetts, announced that they had cloned the first human embryos in November 2001.
This was done by collecting eggs from women's ovaries, removing the genetic material
from inside using a needle less than 1/5,000 of an inch wide, and inserting a skin cell
inside the enucleated egg to serve as a new nucleus. After the egg was stimulated with
ionomycin, it began to divide. Results were limited in success--although the process was
carried out with eight eggs, only three began dividing, and in the end only one was able
to divide into six cells before stopping.
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