As stated earlier, the cloning process has been around for many years. Twins, produced by sexual reproduction, have identical nuclear DNA and identical mitochondrial DNA. In a laboratory setting, the embryo is mechanically divided allowing the cells to grow and develop separately. “Twinning is also referred to as embryo cloning” (15).
“Gene splicing is a method of cloning in which pieces of genes or whole genes are inserted into bacteria. The bacteria multiply and make large amounts of the protein called for by the newly inherited gene”(16). Dr. David Jackson pioneered gene splicing. His research with viral and bacterial cells provided scientists with tremendous capabilities in terms of genetically engineering specific host cells especially in his explanation of breaking DNA molecules into much smaller pieces. This contributed to a wide interest in how genetic materials of viruses can be turned on and off, making huge numbers of offspring. “The Recombinant DNA Technology allows researchers to simply snip out pieces of DNA, splice them into bacteria and clone them in huge quantities”(17). The fusion of the DNA samples is aided by plasmids. “Plasmids “are ring-shaped pieces of DNA and are the vehicles by which some bacteria inject some of their DNA directly into other bacteria when they mate in a process called conjugation” (18).
Plants also go through a cloning process. This type of cloning is done either naturally through stem cutting or by using laboratory methods. Using the lab methods scientists isolate single cells and provide appropriate conditions necessary for them to divide and form numerous cells that make up young plants. The method known as “tissue culture” uses hormones and certain growing conditions to produce clones (19).
Another method of cloning is through a process known as nuclear transfer. The nucleus of an egg cell is removed from a host animal and replaced with a cell nucleus from a different adult animal. Next the egg cell with the transferred nucleus is placed into the host animal’s reproductive system. This cell now has all of the capabilities needed to develop into an exact genetic replica. An experiment performed by John Gurdon in the early 1950’s used this process to clone the cells of tadpoles. Although the embryos never developed beyond the tadpole stage, this experiment illustrated that technology and perseverance would enable scientists to move forward in their research. In the 1970’s this technique was used to clone mice. Unsuccessful attempts at cloning followed until the research of Steen Willardon, an employee at the Granada Genetics, Inc. used the nuclear transfer method to produce calves from embryos. The embryos progressed to the 64 and 128-cell stage and confirmed the possibility of successful nuclear transfers in mammals (20).
Finally in 1995, Ian Wilmut, a Scottish scientist and his colleagues produced Megan and Morag, two live lambs whose embryos had been cultured for months in the laboratory. This set the stage a couple of years later when the world was introduced to Dolly, the first successfully cloned mammal. Dolly was cloned from a cell belonging to an adult animal. Cells were taken from the udder of a 6-year-old Finn Dorset ewe. These cells were cultured in a lab and then fused with unfertilized eggs from which the genetic material was removed. Two hundred and seventy-seven “reconstructed eggs” were cultured in temporary recipients. Twenty-nine eggs, which appeared to have developed normally, were implanted into thirteen surrogate Scottish Blackface ewes. One hundred and forty-eight days later, Dolly was born and later introduced to the world.