The Polymerase Chain Reaction Association （聚合酶链反应协会）.pdf

A series of articles for general audiences The Polymerase Chain Reaction By Tabitha M. Powledge It is hard to exaggerate the impact of the polymerase chain reaction. PCR, the quick, easy method for generating unlimited copies of any fragment of DNA, is one of those scientific developments that actually deserves timeworn superlatives like revolutionary and breakthrough. First described only 10 years ago, in its short life PCR has transformed the life sciences utterly. From the daily practicalities of medical diagnosis to the theoretical framework of systematics, from courts of law to field studies of animal behavior, PCR takes analysis of tiny amounts of genetic material-even damaged genetic material-to a new level of precision and reliability. PCR is the most important new scientific technology to come along in the last hundred years, says Mark R. Hughes, deputy director of the National Center for Human Genome Research at the National Institutes of Health (perhaps better known as the Human Genome Project). And Science has pointed out that, because it is far simpler and less expensive than previous techniques for duplicating DNA, PCR has democratized genetic research, putting it within reach of all biologists, even those with no training in molecular biology. WHAT IS PCR? The central scientific fact that makes PCR so useful is this: The genetic material of each living organism-plant or animal, bacterium or virus-possesses sequences of its nucleotide building blocks (usually DNA, sometimes RNA) that are uniquely and specifically present only in its own species. Indeed, complex organisms such as human beings possess DNA sequences that are uniquely and specifically present only in particular individuals. These unique variations make it possible to trace genetic material back to its origin, identifying with precision at least what species of organism it came from, and often which particular mem