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In genetics, somatic cell nuclear transfer (SCNT) is a technique for cloning.
The process
The nucleus of a cell contains DNA, which acts roughly as its blueprint (although 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 the nucleus of a somatic cell (a cell other than a sperm or egg cell) is removed and the rest of the cell is discarded. In parallel, the nucleus of an egg cell is removed. The nucleus of the somatic cell is then inserted into the denucleated egg cell. The egg, now containing the nucleus of a somatic cell, is stimulated in such a way that it begins to divide.
This technique is currently the basis for cloning animals, such as the famous Dolly the sheep, and could theoretically be used to clone humans. Scientists at the Harvard Stem Cell Institute are currently researching a technique to use somatic cell nuclear transfer to produce embryonic stem cells. In 2005, a South Korean research team led by Professor Hwang Woo-suk, published claims to have achieved embryonic stem cell cloning, and supported those claims with fabricated data. Embryonic stem cells are created by performing somatic cell nuclear transfer using a somatic cell (usually a skin cell) from the patient or research subject. They are harvested when the egg has undergone cell division and formed a blastocyst. The resulting cells would be, ideally, genetically identical to the original, allowing doctors to tailor stem cell treatments to individual patients avoiding any complications from immune system rejection.
Limitations
The stresses placed on both the egg cell and the introduced nucleus are enormous, leading to a high loss in resulting cells. As the procedure currently cannot be automated, but has to be performed surprisingly manually under a microscope, SCNT is very resource intensive.
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.
"Somatic cell nuclear transfer"