Cloning refers to the development of offspring that are genetically identical to their parent. Animals which reproduce asexually are examples of clones that are produced naturally.
Thanks to advances in genetics, however, cloning can also occur artificially by using certain cloning techniques. Cloning techniques are laboratory processes used to produce offspring that are genetically identical to the donor parent.
Clones of adult animals are created by the processes of artificial twinning and somatic cell nuclear transfer. There are two variations of the somatic cell nuclear transfer method. They are the Roslin Technique and the Honolulu Technique. It is important to note that in all of these techniques the resulting offspring will be genetically identical to the donor and not the surrogate unless the donated nucleus is taken from a somatic cell of the surrogate.
Somatic Cell Nuclear Transfer
The term somatic cell nuclear transfer refers to the transfer of the nucleus from a somatic cell to an egg cell. A somatic cell is any cell of the body other than a germ cell (sex cell). An example of a somatic cell would be a blood cell, heart cell, skin cell, etc.
In this process, the nucleus of a somatic cell is removed and inserted into an unfertilized egg that has had its nucleus removed. The egg with its donated nucleus is then nurtured and divides until it becomes an embryo. The embryo is then placed inside a surrogate mother and develops inside the surrogate.
The Roslin Technique
The Roslin Technique is a variation of somatic cell nuclear transfer that was developed by researchers at the Roslin Institute. The researchers used this method to create Dolly. In this process, somatic cells (with nuclei intact) are allowed to grow and divide and are then deprived of nutrients to induce the cells into a suspended or dormant stage. An egg cell that has had its nucleus removed is then placed in close proximity to a somatic cell and both cells are shocked with an electrical pulse. The cells fuse and the egg is allowed to develop into an embryo. The embryo is then implanted into a surrogate.
The Honolulu Technique
The Honolulu Technique was developed by Dr. Teruhiko Wakayama at the University of Hawaii. In this method, the nucleus from a somatic cell is removed and injected into an egg that has had its nucleus removed. The egg is bathed in a chemical solution and cultured. The developing embryo is then implanted into a surrogate and allowed to develop.
While the previously mentioned techniques involve somatic cell nuclear transfer, artificial twinning does not. Artificial twinning involves fertilization of a female gamete (egg) and separation of resulting embryonic cells in the early stages of development. Each separated cell continues to grow and can be implanted into a surrogate. These developing embryos mature, eventually forming separate individuals. All of these individuals are genetically identical, as they were originally separated from a single embryo. This process is similar to what happens in the development of natural identical twins.
Why Use Cloning Techniques?
Researchers hope that these techniques can be used in researching and treating human diseases and genetically altering animals for the production of human proteins and transplant organs. Another potential application includes the production of animals with favorable traits for use in agriculture.