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Cloning is the production of duplicate copies of genetic material, cells, or entire multicellular living organisms. The copies are referred to as clones. Cloning occurs naturally and is also engineered by human beings. The possibility that people might be cloned from the cells of a single adult human being had long been a subject primarily of fantasy and science fiction but became very definite at the end of the 20th century. This possibility stemmed from the successful cloning of lower mammals, leaving little doubt in many scientists’ minds that humans could and would one day be cloned.

Cloning takes place in plants and animals, which become known as master cloners. The fertilized egg from which a human develops, for example, contains DNA from both mother and father. The egg divides into two identical cells, then four, then eight, and so on. These cells are clones and so is the DNA within them, because it, too, is copied into every cell that is produced. In time, the cells begin to differentiate, or become specialized, into skin cells, eye cells, liver cells, and so on. They still are a single clone with respect to their DNA, each cell having the same DNA as the original fertilized egg. But much of the DNA that constitutes many of the genes becomes inactive. The active genes are the only ones needed by each type of specialized cell to stay alive and perform its specific functions. Then, as these specialized cells multiply and organize to form their special organs and other structures, even more clones of millions of cells are formed. In this sense, most living things are mainly groups of cloned cells. As organisms grow, heal after injury that destroys cells, and replace cells that die naturally, organisms clone cells and their DNA for the rest of their lives.

As scientists drew closer to the day when it would be possible to clone humans, many people began to express fears associated with the prospect. The decision to clone humans, even for the “betterment” of the species, raises the issues of who would be the ideal candidates for cloning and what characteristics should be duplicated. Among some of the issues debated are whether extreme intelligence or great athleticism should be more valued; creativity or stability; health or sensitivity. Even more are the issues of who will be the people to decide what traits are valuable and which people are chosen to be cloned, if cloning humans becomes possible and acceptable. The issue of cloning is a widely discussed topic in today s society.

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