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RATS have suddenly become a little more appealing, for geneticists at least.

The rodents are used extensively in medical research. But while geneticists can disrupt or 鈥渒nock out鈥� both copies of genes in mice, the techniques used to create knock-out mice have not proved effective in rats.

So researchers at the University of Wisconsin-Madison developed a new method. They injected male rats with mutagenic chemicals and studied their offspring for disruption in two genes associated with breast cancer, Brca1 and Brca2 (Nature Biotechnology, DOI: 10.1038/nbt830). Rats carrying defective copies of the gene were then mated to create animals with two disrupted copies. The technique is flexible enough to work for any gene.