SCNT technique for cloningScientists modify somatic cell nuclear transfer technique to generate pluripotent stem cells
In genetics and developmental biology, somatic cell nuclear transfer (SCNT) is a laboratory technique for creating an ovum with a donor nucleus. In SCNT the nucleus, which contains the organism's DNA, of a somatic cell (a body cell other than a sperm or egg cell) is removed and the rest of the cell discarded. This phenomenon is also called nuclear transfer, uses a different approach than artificial embryo twinning, but it produces the same result: an exact genetic copy, or clone, of an individual. This was the method used to create Dolly the Sheep. If we expand the term “Somatic cell nuclear transfer”; the definitions are as follows and if we combine all these, the process involved in SCNF is clear!
Somatic cell: A somatic cell/vegetal cell (soma = body) is any cell in the body other than sperm and egg, the two types of reproductive cells/germ cells. If the process of germ cells is produced through meiosis, somatic cells are produced through the process of mitosis and cytokinesis. This continues to replace and generate old and damaged cells. If germ cells only contain one set of chromosomes, a somatic cell has a diploid number of chromosomes.
Nuclear: The nucleus is a compartment that holds the cell's DNA. The DNA is divided into packages called chromosomes, and it contains all the information needed to form an organism and the small differences in our DNA that make each of us unique.
Transfer: Moving an object from one place to another. To make Dolly, researchers isolated a somatic cell from an adult female sheep. Next they removed the nucleus and its entire DNA from an egg cell. Then they transferred the nucleus from the somatic cell to the egg cell. This process involves the nucleus of an egg cell, replacing it with the material from the nucleus of a "somatic cell" (a skin, heart, nerve or any other non-germ cell), and stimulating this cell to begin dividing. This egg cell is never fertilized by sperm, and the genetic material within the cell is virtually identical to the genetic material extracted from the skin or other cell. After a couple of chemical tweaks, the egg cell, with its new nucleus, was behaving just like a freshly fertilized egg. It developed into an embryo, which was implanted into a surrogate mother and carried to term. (The transfer step is most often done using an electrical current to fuse the membranes of the egg and the somatic cell.)
Thus, SCNT is a technique for cloning. The nucleus is removed from a healthy egg. This egg becomes the host for a nucleus that is transplanted from another cell, such as a skin cell. The resulting embryo can be used to generate embryonic stem cells with a genetic match to the nucleus donor (therapeutic cloning), or can be implanted into a surrogate mother to create a cloned individual, such as Dolly the sheep (reproductive cloning). The lamb, Dolly, was an exact genetic replica of the adult female sheep that donated the somatic cell. She was the first-ever mammal to be cloned from an adult somatic cell.