Just like taste, it’s really common for people not to agree on how pleasant or fowl a scent may be. You might find the meal you just cooked to have a pleasant odor or you might have bought a perfume you thought smelled divine, only for some other person to disagree and express a distaste. Apparently, according to researchers at Duke University, no two people have the exact sense of smell, meaning the way you perceive the odors around you is unique.
That’s not to say, of course, that everybody has a dramatically different perception over smell – most common smells are easily recognizable and perceived more or less similarly. It’s those subtle variations, which in some cases lead to opposite standing contradictions, that cause uniqueness.
The way you smell, like any other biological functions, is governed by your genes. Humans can distinguish more than 10,000 different smells (odorants), which are detected by specialized olfactory receptor neurons lining the nose. Some 400 genes have been discovered so far coding the receptors in our noses, and according to the 1000 Genomes Project, there are more than 900,000 variations of those genes. When a odor (molecule) binds to these receptors, a specific signal is sent to the brain, processed and retrieved as smell.
The missense of smell
According to Hiroaki Matsunami, Ph.D., associate professor of molecular genetics and microbiology at the Duke University School of Medicine, the receptors in any two people should be 30% different. What this means is that people actually perceive smell quite differently, judging from this figure. Also, promoter regions of the genes, which are highly variable, or gene copy number variation, which is very high in odor receptors, weren’t taken into account so actually 30% is a conservative appreciation.
“There are many cases when you say you like the way something smells and other people don’t. That’s very common,” Matsunami said. But what the researchers found is that no two people smell things the same way. “We found that individuals can be very different at the receptor levels, meaning that when we smell something, the receptors that are activated can be very different (from one person to the next) depending on your genome.”
Previously, scientists discovered the genes that encode the smell receptors, however it was rather unclear how these receptors worked in response to odors. Mastunami and colleagues cloned more than 500 receptors each from 20 people that had slight variations of only one or two amino acids (the smallest difference in DNA), then systematically exposed these to various chemicals to see how these bonded to the receptors.
The various odorants, like vanillin or guaiacol, were released in incremental concentrations – 1, 10 and 100 micromoles – and in doing so, the researchers identified 27 receptors that had a significant response to at least one odorant.
The findings, reported in a paper published in Nature Neuroscience, could influence the flavors, fragrance, and food industries.
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“These manufacturers all want to know a rational way to produce new chemicals of interest, whether it’s a new perfume or new-flavored ingredient, and right now there’s no scientific basis for doing that,” he said. “To do that, we need to know which receptors are being activated by certain chemicals and the consequences of those activations in terms of how we feel and smell.”