Cloning
On February 24, 1997, the scientists at the Roslin Institute in Edinburg, Scotland announced their success in cloning an adult mammal for the first time. The cloned sheep was named Dolly. She was the first animal cloned from a cell taken from an adult. It was an accomplishment than science had declared impossible. In June, 1997, the National Bioethics Advisory Commission issued its recommendation that a ban be placed on all efforts to create a child through cloning or "somatic cell nuclear transfer." They urged that the current moratorium on federal funding of human cloning research be continued, and requested private agencies also restrain from such work. At the same time they recommended that this issue be reevaluated after a 3-5 year period of study and reflection. Dolly was a clone of the sheep (her genetic mother) who provided the udder cell. The package of genes in the nucleus of that udder cell contained exactly the same repertoire of genes as all the rest of her mother's cells and so Dolly's genetic makeup was identical to her mother's. What was novel about Dolly was that she was the first unequivocal mammalian clone. Lower vertebrates had been cloned in the early 1960s when it was shown that a nucleus taken fro
One way to clone is by cloning from mRNA. This method converts mRNA to DNA (also called copy DNA or cDNA). It uses the enzyme reverse transcriptase to produce complementary DNA. However, there are a few problems with cloning from mRNA. One of them is that the synthesis of full-length cDNAs may be inefficient, particularly if the mRNA is relatively long. More recent methods can overcome this problem. Another method is cloning cDNA in plasmid vectors. Scientists prefer using the bacteriophage vector system, but plasmids are still often used when isolation of the desired cDNA sequence involves screening a small number of clones. California banned human cloning. Meanwhile, the real action was quietly going on in the laboratories, outside the periphery of the public eye. Federally supported experiments in cloning monkeys for use in AIDS vaccine and other research was continuing outside the limelight. What can be done with monkeys can probably be done with people. "We are laying the groundwork," one of the scientists said. (Gin Kolata, New York Times) Scientists made a number of advances in cloning in 1998. In December, biologists in Japan said they had used a cloning technique to produce eight identical calves from cells removed from an adult cow. In July, researchers at the University of Hawaii announced that they had created more than 50 mice through cloning by using cells from adult mice. An apparent advance on the Roslin technique was reported in August 1997, when scientists at ABS Global Incorporated in DeForest, Wisconsin, a biotechnology company specializing in livestock reproductive services, said that they had produced a calf using a cloning procedure more efficient than that used with Dolly. The Wisconsin scientists began by performing a nuclear transplantation to produce an embryo from a body cell of a 30-day-old bull fetus Then they added another step. They took one of the cells from the embryo they had produced and performed a second nuclear transplantation. The embryo resulting from
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