UNITED KINGDOM - NOVEMBER 14: These male mice are direct descendants of the first transgenic mammals to be granted a US patent. This strain was patented by Harvard University Medical School in 1988. Their genes were altered to make the mice more prone to develop cancers by the insertion of an extra piece of DNA taken from a virus; a trait which makes this strain of mouse (known as the 'oncomouse') particularly useful in cancer research. (Photo by SSPL/Getty Images)
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