OUR sense of smell is gradually deteriorating with the passing generations.
快猫短视频s 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.
鈥淭hough 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鈥檛 work is probably
growing,鈥� 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.
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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鈥� DNA suggested that 72 per cent of them have mutated in such a way
that they no longer work. Giorgi concludes in this month鈥檚 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, or at some earlier point in life鈥檚 history.