办事指南

Why dogs can turn up their noses at their masters

点击量:   时间:2017-07-22 01:02:08

By Michael Day OUR sense of smell is gradually deteriorating with the passing generations. Scientists say that more than 70 per cent of the genes that code for olfactory receptors, the proteins that enable us to smell, have mutated to the point of being useless. “Though humans will continue to have a significant sense of smell for a very long time yet, I think the number of these genes that don’t work is probably growing,” says the team leader Dominique Giorgi of the Research Centre for Macromolecular Biochemistry in Montpellier, France. With his colleague Barbara Trask of Washington University in Seattle, Giorgi hoped to hunt down the smell receptor genes in the human genome. Previous research suggested our sense of smell relies on around 1000 different receptors, and that the genes that code for them contain large stretches of identical DNA. The team used probes sensitive to these sequences to find some of the genes, which turned out to be dotted across most of our 46 chromosomes. Their analysis of the genes’ DNA suggested that 72 per cent of them have mutated in such a way that they no longer work. Giorgi concludes in this month’s Nature Genetics (vol 18, p 243) that our ancestors had more sophisticated genetic machinery for smell; over time this has deteriorated. Giorgi suspects that the results reveal a striking example of rapid genetic evolution. By comparing the olfactory gene sequences with those in dogs and primates, he hopes to confirm whether the mutations took place during human evolution,