Somatic cell nuclear transfer

From Free net encyclopedia

In genetics, somatic cell nuclear transfer (SCNT) is a technique for cloning.

The process

Image:Cloning-cell.jpg 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 the cell is discarded. In parallel, the nucleus of an egg cell is removed. The nucleus of of the somatic cell is then inserted into the denucleated egg cell.

This technique is currently the basis for cloning animals, such as the famous Dolly the sheep, and could theoretically be used to clone humans. It is 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.

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.de:Zellkerntransfer