共用题干 第一篇Can Gene Technology Make Human Smarter?Almost everyone wants to get smarter. To achieve that,some choose to do exercise,others choose to take in more nutritions good for brains.Princeton neurobiologist Joseph Z.Tsien possibly found a different way to make it. In September he announced that he'd built a better mouse by altering a gene that affects learning and memory.A similar process of gene manipulation might conceivably be used one day to boost intelligence in humans.The key of this technology lies in a feature of brain cells called the NMDA receptor,which Tsien likens to a cylindrical tube or window that mediates the flow of information.When the window is open,chemicals called neurotransmitters flow through easily and memory is registered and stored. But as organisms mature,the window begins to close.(This may explain why children lose their facility for learning new languages when they reach sexual maturity and why some people suffer memory loss as they age.)Tsien also found out that the receptor worked more efficiently if it is teamed with the gene NR2B,so he introduced extra NR2B genes into a batch of fertilized mouse eggs.In a normal mouse,the memory window is open for just 150-thousandths of a second.In Tsien's specially engineered mice,the window opens for 250-thousandths of a second,long enough to make a remarkable difference in memory retention.When he pitted his mice against common mice,they won paws down.Ordinary mice could recognize a Lego block for 12 hours,but smart mice could remember the block for up to three days."That's a profound enhancement,"Tsien says.Can this technology be applied to humans?Maybe,but genetic engineering will have to make some extraordinary advances first. And some thorny ethical issues will have to be resolved. Mean-while,Tsien promises to keep his furry little geniuses locked up in a lab,far from your larder. "Otherwise,"he says,"you might need a smart cat or a smart mousetrap to catch them." According to the passage,what special method did Tsien find to make a smarter mouse?
A.By controlling the flow of information. B.By making some change in a gene that affects learning and memory. C.By pitting his mice against common mice. D.By keeping a genetically modified cat.正确答案B
