The possibility of cloning humans was raised when Scottish scientists at the Roslin Institute in Scotland created the highly celebrated sheep “Dolly.” This and other cloning movements have aroused worldwide interest and concern due to the scientific and ethical implications. The development that has been quoted as the advancement of the decade by many scientists and analysts has brought with itself the ambiguity over the meaning of the term “cloning.” This term was used as having an all inclusive definition to represent several processes for duplicating biological material. In relation to the Human Genome Project and similar research, cloning implies the copying of genes and other pieces of chromosomes to generate enough identical material for further study. At this time there are two types of cloning procedures or techniques that produce complete, genetically identical animals.
1. Blastomere separation- This technique is sometimes also called “twinning.” This term comes after the naturally occurring process that creates identical twins. The technique involves the splitting of a developing embryo soon after fertilization of the egg by a sperm (sexual reproduction).This gives rise to two or more embryos. The resulting organisms are identical twins (clones) containing DNA from both the mother and the father.
2. Somatic cell nuclear transfer-Dolly was the result of another type of cloning. The technique produces animals carrying the DNA of only one parent. Using somatic cell (All cells that are not egg or sperm cells are somatic cells) nuclear transfer, scientists transferred genetic material from the nucleus of an adult sheep’s udder cell to an egg whose nucleus, and thus its genetic material, had been removed.
One of the main goals of this and similar research is to develop efficient ways to alter of animals genetically and reproduce them reliably. Alterations have included adding genes, such as those for human proteins. This technique makes it possible to create drug-producing animals. In addition to this, it enables scientists to inactivate genes to study the effects and possibly create animal models of human diseases. The other promise of cloning technology is that it may someday be used in humans to produce whole organs from single cells or to raise animals having genetically altered organs suitable for transplanting to humans.
The technique used to produce Dolly and other cloned animals is an extension of 40 years of research using DNA from non-human embryonic and fetal cells. Before this demonstration, scientists believed that once a cell became specialized a liver, heart, udder, bone, or any other type of cell the change was permanent and other unneeded genes in the cell became inactive. Dolly’s creators demonstrated that a nucleus of an adult animal’s specialized cells can be made to revert to a non-specialized, embryonic state. This implies that the cell has the ability to restore its capacity to give rise to any kind of cell. Explorations into how cells revert to an undifferentiated state may provide insights into the process by which cells become cancerous.
Using the same technique that produced Dolly, researchers have cloned a number of large and small animals. This includes sheep, goats, mice and cows. But scientists remain uncertain about whether genetic changes in the cells used to obtain nuclei will lead to adverse effects on the health of the cloned animals.