Science Fair Project Encyclopedia
Somatic cell nuclear transfer
The nucleus of a cell contains DNA, which acts roughly as its blueprint (unlike an actual blueprint, these instructions are greatly affected by environment as well as other factors not yet fully understood, and can change over time.) In somatic cell nuclear transfer, known more simply as SCNT, the nucleus of an unfertilized egg is removed. The nucleus of a somatic cell -- i.e., a cell other than a sperm or egg cell, such as a skin or nerve cell -- is then removed and put in the emptied egg.
This technique is the basis for cloning animals, such as the infamous Dolly the sheep , and -- theoretically -- humans. It is more commonly used to produce embryonic stem cells. In order to do this, the egg, now containing the nucleus of a somatic cell, is stimulated in such a way that it begins to divide. The resulting cells are, ideally, genetically identical to the original; embryonic stem cells are harvested when dividing cells have formed a blastocyst.
The stress placed on both the egg cell and the introduced nucleus are enormous, leading to a high mortality rate in resulting cells. As the procedure currently cannot be automated, but has to be performed manually under a microscope, SCNT is very resource-consuming.
The biochemistry involved in "activating" the recipient egg is far from understood.
Not all of the donor cell's genetic information is transferred. DNA of organelles (mostly mitochondria) is left behind, with the resulting cells retaining those structures which originally belonged to the egg.
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