CLONING WHAT IS IT
Cloning is the production of one or more individual plants or animals that are genetically identical to another plant or animal. Nature itself is the greatest cloning agent. In about one of every 75 human conceptions, the fertilized ovum splits for some unknown reason and produces monozygotic (identical) twins. Each has a genetic makeup identical to the other. Two very different procedures have been referred to as "cloning": · Embryo cloning has been successfully carried out for years on many species of animals. Some limited experimentation has been done on human embryos. · Adult DNA cloning has been used to clone a sheep, but was not tried on humans until December 1998. Human embryo cloning starts with a standard in vitro fertilisation procedure. Sperm and an egg cell are mixed together on a glass dish. After conception, the zygote (fertilised egg) is allowed to develop into a blastula (a hollow mass of cells). The zygote divides first into two cells, then four, then eight... A chemical is added to the dish to remove the "zona pellucida" covering. This material provides nutrients to the cells to promote cell division. With the covering removed, the blastula i
· Have an impact on the decline in genetic variety With the exception of the sperm and egg, every cell in the body contains all of the genetic material in its DNA to theoretically create an exact clone of the original body. But cells have been "biochemically programmed to perform limited functions." The other functions are turned off. Most scientists had believed that such differentiated cells could not be reprogrammed to be capable of behaving as a fertilized egg. · Taking God's work into our own hands In the case of the sheep "Dolly", a cell was taken from mammary tissue of a mature 6 year old sheep while its DNA was in a dormant state. It was fused with a sheep ovum which had had its nucleus removed. The "fertilised" cell was then stimulated with an electric pulse. Out of 277 attempts at cell fusion, only 29 began to divide. These were all implanted in ewes. 13 became pregnant but only one lamb, Dolly, was born. Cloning has had a fairly long history:
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Approximate Pages = 3 (250 words per page double spaced)
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