The word "cloning" generally conjures up images of armies of identical people, grown in huge test tubes, marching onward to some evil purpose. In reality, however, cloning is not nearly so sinister. Cloning simply refers to making identical copies of something from one unit. Usually when scientists talk about cloning, they refer to DNA, bacteria, or cells. Cloning bacteria is simple. It is done by separating bacteria out so that only one bacterium is present. This bacterium will divide and form a colony of millions, all of which are identical to the first one. Since they are identical, they are clones. DNA is cloned a little bit differently. Cloning DNA means making an exact copy of some part of the DNA that is of interest. This could be a gene, for example. That copy is then amplified into many copies. Since each one is identical, they are called cDNA, short for cloned DNA.
It is also possible to clone organisms bigger than bacteria. Plants are sometimes easy to clone. Certain types of plant cells, if treated properly, will grow into entire new plants, identical to the original plant on a genetic level. Animals are harder to clone, but it is very possible to clone them. Animals can be naturally cloned in the case of twins. With identical twins, the fertilized egg separates and grows to make two embryos instead of just one. This makes them clones, since they are genetically identical. Scientists have been able to duplicate this process in animals for a long time. A more important method of cloning is called somatic cell cloning. In this method, DNA from an adult animal is used to make a new organism. Basically an identical twin is created from an adult. This is much more difficult to do, because as animals grow and develop different organs and tissues, the DNA in those tissues is modified. Some DNA is locked up, unable to be used in different parts of the body. In order to make a complete cloned animal, however, all of the DNA must be accessible. Scientists conquered this challenge, and the first somatically cloned sheep was made in Scotland in the year 1997. Her name is Dolly.
Dolly was made by taking the DNA from her mother and putting it into a sheep egg cell that had had the DNA removed. This cell was then implanted in a normal sheep uterus and grew just like a normal embryo. Therefore, even though Dolly is a clone of her mother, she is several years younger. This is important to understand. Clones are not grown in tanks by scientists in labs. They do not emerge fully grown. There has been much discussion about human cloning recently. Because it is possible to clone sheep and other mammals, it should be possible to clone a human being. However, there are very serious ethical considerations to consider. It may be possible to clone yourself, and therefore have a supply of perfectly matched organs for transplantation. However, it is probably not ethical to create people just to harvest their organs. It may also be possible for such things to happen as a woman to give birth to her twin sister. Because of these unresolved issues and dangers, it is currently not legal for anyone in the United States to clone a human being using government money.