Word: nuclei
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...simplest kind of vegetable cloning consists of cultivating cuttings from a plant. By the mid-1950s scientists had succeeded in cloning amphibians, producing frogs that were genetically identical to each other and carried the inherited characteristics of only a single parent. Most animal cloning has been done by transplanting nuclei into egg cells to produce an entire organism from a single cell. But the cloning of higher forms of life, like mammals, is hard to achieve. Mammal eggs are microscopic, ten to 20 times smaller in diameter than frogs' eggs, and vastly more difficult to manipulate. Consequently, the barriers...
...Geneva and Peter Hoppe of the Jackson Laboratory in Bar Harbor, Me., both veteran researchers in cell biology. Their breakthrough was not in conception -since the procedures for cloning are familiar. It lay rather in the surgeon-like skill and persistence with which they used microscopic instruments to transplant nuclei from cell to cell...
First they scooped a mass of embryonic cells from the womb of a pregnant gray mouse. Using microscopes and a micropipette much finer than a human hair, they sucked out the cells' nuclei and, one by one, transplanted each into a recently fertilized egg extracted from another mouse. That mouse was black and functioned as a kind of genetic control...
...researchers drew out the egg and sperm nuclei that were already in the black mouse's egg so that their genetic information could not influence the resulting clone. Next they cultured the cell in a solution of nutrients until it divided and grew into an early embryo, which was then inserted into the womb of a third mouse, this one white. The white mouse gave birth to a gray mouse, genetically identical to the original embryo...
...Berlin, he and Colleagues Jon Gordon and George Scangos isolated genes from two viruses and manufactured them in large quantities. Then, guided by a high-powered microscope and using tubes thinner than hairs, they delicately microinjected 1,000 to 20,000 copies of the genetic material directly into the nuclei of newly fertilized mouse eggs kept alive in laboratory dishes. The eggs were then carefully transferred to the wombs of female mice and eventually the foster mothers gave birth to 150 infants. The newborns were promptly killed, and the DNA was extracted from their tissues for study. Portions...