Word: dna
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...store mice. Others are clearly extraordinary, waddling about on paws shaped like miniature dolphin flippers or swollen to the size of their larger relative, the rat. They are called transgenic mice, and in a nobly selfless fashion, they are revolutionizing modern biology. Hidden somewhere along the twisting chain of DNA found in every cell of their bodies are alien genes, injected by biologists. The study of these mutants and the effects of the interloping genes may help provide answers to such fundamental questions as what switches DNA on and off, and how a single cell blossoms into a complex organism...
Their strategy worked beautifully. The growth-hormone gene was incorporated into the DNA of about a third of the mouse pups and, most important, was activated in a variety of tissues. These offspring, spurred on by the extra portion of growth hormone, ballooned to twice the size of normal mice. What is more, because the new gene was present in all their cells, including their sex cells, it was passed along to the next generation. Says Brinster: "We're now doing work on the seventh generation of Supermouse...
...somewhat subtler series of experiments, Baltimore and his colleagues are studying how genes for disease-fighting antibodies are coordinated to respond to thousands of different invading microbes. They tailor-made a mouse gene for producing antibodies and inserted it into the DNA of a normal mouse. Although the antibody gene was bequeathed to every cell of the transgenic mouse, it was turned on (expressed) only where antibody genes normally operate: in the white blood cells. Now the scientists can determine just what gives the gene a preference for one tissue type over another, a crucial step in determining how cells...
...understand better the genetic basis of cancer, Philip Leder, a molecular geneticist at the Harvard Medical School and his colleague Timothy Stewart, have bred a line of transgenic mice that may someday serve as a model for human breast malignancy. He designed a DNA hybrid consisting of a gene called c-myc, which has been implicated in animal and human cancer, linked to a regulatory segment of another gene that is expressed in developing and lactating breast tissue. Soon after female mice with the injected gene give birth and begin nursing, they grow sizable tumors in their breasts. Perhaps more...
...turns out the remains might have been Yokota's after all. In February, the British scientific journal Nature published an article in which the scientist who did the tests admitted they were inconclusive-and that the remains could have been contaminated with foreign DNA. "The bones are like stiff sponges that can absorb anything," Teikyo University DNA analyst Yoshii Tomio told a Nature interviewer. The technique Yoshii used, known as "nested PCR," also raised doubts: professional forensics labs in the U.S. don't use it because of the high risk of contamination, according to Terry Melton, a DNA expert...