Could we use embryo for clonning?

Let's discuss (3) techniques:

• Blastomere Separation
• Blastocyst Division
• Somatic Cell Nuclear Transfer

A. Blastomere Separation

In blastomere separation, scientists fertilize an egg cell with a sperm cell in a laboratory dish. The resulting embryo is allowed to divide until it forms a mass of about four cells. Scientists remove the outer coating of the embryo and place it in a special solution that causes the individual cells of the embryo, known as blastomeres, to separate. Scientists then put each blastomere in culture, where it forms an embryo containing the same genetic makeup as the original embryo. Each new embryo can then be implanted into the uterus of a surrogate mother to develop during a normal pregnancy.

B. Blastocyst Division

In blastocyst division, scientists allow a fertilized egg to divide until it forms a mass of about 32 to 150 cells, known as a blastocyst. Scientists then split the blastocyst in two and implant the two halves into the uterus of a surrogate mother. The two halves develop as identical twins.

C. Somatic Cell Nuclear Transfer

While blastomere separation and blastocyst division produce animals containing the genetic material from both a mother and father, somatic cell nuclear transfer produces an animal carrying the genetic material of only one parent. In this technique, scientists transfer the genetic material from a donor’s somatic cell (any body cell other than an egg or sperm cell) to an enucleated egg cell—that is, an egg cell with its nucleus, and thus its genetic material, removed. The resulting cloned cell contains the genetic material of the donor’s somatic cell.

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Scientists merge the somatic cell and enucleated egg cell using fusion or injection. In the fusion method, scientists place a somatic cell in contact with an enucleated egg cell. An electric pulse applied to the two cells pushes the somatic cell’s nucleus into the enucleated egg cell. With the injection method, scientists inject the somatic cell’s nucleus directly into the enucleated egg cell. 

In early experiments with somatic cell nuclear transfer, the procedure only worked using the nuclei from embryonic cells or cells from immature animals. In 1996 British scientists produced the sheep Dolly using a variation of somatic cell nuclear transfer that used the nuclei from adult cells. Scientists treated the adult donor cell to make it quiescent (less active) so that the genes of the adult cell behaved more like an undifferentiated embryo cell. They then isolated an udder cell from an adult sheep and starved the cell, forcing it into a resting stage that prevented the nucleus from dividing. Scientists found that this resting stage helps the adult cell return to an embryonic state. Scientists transferred the genetic material from the nucleus of the adult udder cell to an enucleated egg cell from a second sheep. The resulting embryo was then implanted into the uterus of a third sheep, where it developed during a normal pregnancy.

The birth of Dolly paved the way for cloning cells taken from adult animals, enabling scientists to choose the mature individual they want to duplicate. Using cells from immature animals makes it more difficult for scientists to predict with certainty the physical characteristics of the resultant clone. 

Somatic cell nuclear transfer only uses genetic material found in a donor cell’s nucleus. But not all of an animal’s genes are located in the nucleus. A few dozen genes reside in the mitochondria, a cell structure found outside of the nucleus in the cell’s cytoplasm. As a result, clones derived from somatic cell nuclear transfer may have mitochondrial genes from the enucleated egg cell used in the cloning process, not just genes from the donor’s genetic material. 

In addition, since every organism is influenced by the interaction of both genes and the environment, cloned organisms may exhibit certain characteristics that differ from the genetic donor. A cloned animal, for instance, inevitably experiences many environmental factors during its development that differ from the parent’s experience. These factors may include the types and quantity of food available, exposure to infectious diseases, or even the position of the embryo as it develops in the surrogate mother's womb.