How It Works

Delve into the process of cloning.

Somatic Cell Nuclear Transfer

Somatic Cell Nuclear Transfer, or SCNT for short, is the process by which animals (including livestock) are cloned currently (scientists went from using embryonic cells to somatic cells - read more about that here). Simply put, during SCNT, the nucleus of a somatic cell (which is any cell not involved in reproduction, such as a skin cell) is transferred to an egg cell. Let's look at this process more in depth: (C-2.1)

A somatic cell is removed from the animal that will be cloned.
The nucleus (including DNA) is removed from an egg cell (a reproductive cell).
The nucleus from the somatic cell is transferred into the egg cell that was previously emptied of its genetic elements (known as an enucleated cell). This can happen in two ways:
1. Researchers can inject the somatic nucleus into the egg with a needle.
2. They can also fuse the somatic cell to the egg with an electric current.
The egg cell, which acts as a freshly fertilized egg, develops into an embryo in a test tube.
This embryo is then implanted in a surrogate mother, who eventually (ideally) gives birth to a genetic clone of the animal from whom the somatic cell came from.

(C-2.2)

The result of this process is a genetically identical clone of the original somatic cell donor. However, the clone won't be exactly the same - the DNA is the same, but the way genes are expressed can stray from the original animal's characteristics. (C-2.3)

M-C.2.1

Consider the case of Dolly the sheep (refer to the diagram on the left). A somatic cell was taken from an adult female sheep's udder, then fused with an empty egg cell to form an embryo. The embryo was placed in a surrogate mother's uterus and eventually became Dolly, a lamb genetically identical to the original female sheep.

The process of animal cloning may be applied to human cloning in the future. Watch the video on the left (Source: M-C.2.2) to learn more about the possible future process of human cloning - the basic principles apply to livestock cloning as well. To explore the ethics of applying SCNT to human cloning, click here.

Challenges and Concerns for the Future

Of course, there are challenges associated with SCNT. Many complications can arise throughout the process, resulting in a low success rate. For example, the embryo may not develop or implant properly in the surrogate mother's uterus. Large Offspring Syndrome (LOS) can occur in cattle and sheep as well. LOS occurs when the "fetus grows too large in the uterus" (C-2.4), which can harm both the developing clone and the surrogate mother. These errors in cloning can be the result of problems in gene expression, as one study conducted by UC Davis shows (C-2.6). The implantation of the embryo into the surrogate mother is an important step in SCNT, so it’s critical that this step goes smoothly. Complications can arise after birth too. Some do have health issues at birth, making them more at risk of dying early. On the positive side, even if a clone has a few minor abnormalities, when he/she grows up, those abnormalities may be indistinguishable. (C-2.4) Considering these challenges, scientists must refine and improve on cloning techniques in order to make cloning safer for animals (read more about animal welfare concerns here).

Cost and the success rate are two major concerns as well. In fact, Mark Walton, the president of ViaGen, stated that "it costs at least $15,000 to clone a cow and $4,000 to clone a sow" (C-2.5). These extremely high prices are the result of how complicated the process of livestock cloning is and the advanced technology that is required. While livestock cloning has potential, the cost will have to lower in the future to increase availability of cloned livestock to farmers. Efficiency must be improved as well. Years before, the success rate was 2-3%, and currently, ViaGen has a 10-15% success rate. While the success rate has improved considerably, it will need to further increase in the future in order to make cloning more viable and efficient. (C-2.5)