Gene manipulation, the linchpin of the "biotechnology revolution," affects almost every level of human existence, from the food we eat and how it is grown; to health care and how it is administered; to how we have babies; and to our perceptions of ourselves, other living things, and nature itself. The term "genetic engineering" was coined in 1965 to denote a range of micromanipulations of the reproductive or hereditary process; that is, manipulations at the level of the cell and of the DNA (genes) within the cells.
Gene manipulation, with its techniques of gene splicing, gene rearranging, and gene cloning, allows scientists to break species boundaries as never before possible. The genes of viruses, bacteria, people, trees, insects, and other living things can be moved into foreign organisms. For instance, a firefly gene has been introduced into tobacco plants to make the mature plants glow. In terms of human genetics, gene manipulation allows scientists to isolate and study genes individually.
Cloning, the production of genetically identical organisms by asexual reproduction (without any combination of egg and sperm cells), is one example of micromanipulation of the reproductive and hereditary processes. By the late 1960s, scientists had successfully cloned a toad by replacing the nucleus of a toad's egg cell with a nucleus of a cell from a mature toad. The toad that grew from the egg was genetically identical to the mature toad whose cell nucleus was used. By 1973, hybrid DNA