Just think of a carbon copy of your mandatory document you get it for the Xerox machine for security or preventive purpose 

To Human Genome Project researchers, cloning refers to copying genes and other pieces of chromosomes to generate enough identical material for further study. Two other types of cloning produce complete, genetically identical animals. Blast mere separation (sometimes called "twinning" after the naturally occurring process that creates identical twins) involves splitting a developing embryo soon after fertilization of the egg by a sperm (sexual reproduction) to give rise to two or more embryos. The resulting organisms are identical twins (clones) containing DNA from both the mother and the father. Dolly, on the other hand, is the result of another type of cloning that produces an animal carrying the DNA of only one parent. Using somatic cell 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. (All cells that are not egg or sperm cells are somatic cells.)