Ewen Callaway, ABC News, June 28, 2009
The vast majority of people in the UK, France, Italy and Russia boast a tandem of genetic variations in a sugar-sensing gene that allows them to detect trace levels of sweetness.
Around the world, populations that live at northern latitudes carry these genetic variations at far higher frequencies than tropical-living peoples, says Dennis Drayna, a geneticist at the National Institute on Deafness and Other Communication Disorders in Bethesda, Maryland.
His team presented 144 Europeans, Asians and Africans with nine solutions containing varying amounts of table sugar–sucrose–in amounts varying from 0 to 4 per cent. “Four-per-cent sucrose is very sweet to everyone, and to me it’s intensely sweet,” Drayna says. “Imagine some cloyingly sweet desert.”
Volunteers arranged the solutions in order of their perceived sweetness numerous times, and from these, Drayna’s team calculated a sucrose sensitivity score for each person.
When the researchers correlated the scores with variations in two sugar-sensing genes, TAS1R3 and TAS1R2, they found two variants just outside of the TAS1R3 gene that seemed to predict their volunteer’s scores.
This puzzled Drayna because TAS1R2 is chock-full of single DNA letter differences between people, and research on bitter taste genes suggested that such mutations–which change the shape of the receptor–underlie these differences.
Instead, the two variations near TAS1R3 probably determine how much of a receptor protein is produced by the taste buds, Drayna says. Tests showed that the variations most common in Europeans crank up the expression of TAS1R3.
Section on Systems Biology of Communication Disorders
Laboratory of Molecular Genetics
5 Research Court, Room 2B-46
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Ph.D., Harvard University, 1981
The Section on Systems Biology of Communication Disorders is focused on identifying genetic variation in the molecular components of human communication systems. Our primary tools are genetic linkage and positional cloning studies, used to identify genes responsible for communication disorders in humans, including deficits in the human sense of taste and the speech disorder of stuttering.
Sweet taste perception: In a study of a group of 150 normal individuals, we’ve recently shown that specific genetic variants, called SNPs, are associated with sweet taste perception. These variants, which are inherited in a simple fashion, explain approximately 16%, or about 1/6th of the difference between individuals in their ability to sense sucrose and other sweet substances. These genetic variants occur in all populations worldwide, but at different frequencies in different populations. The variant forms, which cause reduced ability to taste sweet substances, are most common in African populations. They occur at moderate frequencies in East Asian populations, and lowest frequencies in Western European populations. These differences are related to varying food choices and food preferences, and provide insights into taste perception as well as factors that control our intake of high-calorie sweet foods. Other large-scale studies are currently underway in an effort to identify other genetic variants that affect sweet taste perception.