Odour detection

What is odour detection?

Odour detection, sense of smell, or olfaction: all of these mean your ability to smell. That ability varies from person to person. Each individual smells things differently, and most of these differences are caused by the genetic differences between individuals. Odour receptor genes are one of the largest gene families in our genome [1] Jump to reference section: [1] , but only a few of the genes have so far been linked conclusively to particular smells. As genetic research develops, the link between our ability to smell and our genes continues to grow.

Signs of different odour detection

It is clear that individuals have different reactions to certain smells. The most famous example of this is coriander, with a significant number of people saying that the herb tastes like soap to them [2] Jump to reference section: [2] . What is interesting is that people’s different odour detection has been linked to different genes. Our genes can therefore determine how we smell things. Other examples can be seen in food, plants, and even body odour.

The genetics of odour detection

One of the classic examples of genetics and odour detection is the genetic differences underlying who can smell asparagus in their urine. While people have the ability to smell the trace asparagus, after eating, in their urine, not everyone does [3] Jump to reference section: [3] ‘Asparagus anosmia’, or the inability to smell asparagus in urine is correlated with the genetic variant at rs4481887.People who carry one or more G at this position are less likely to smell asparagus in their urine [4] Jump to reference section: [4] .

See what you carry below:

There are hundreds of different molecules that humans detect with different odours, and we have just scratched the surface on understanding how our perception of these molecules differs. However, some molecules show clear dominant and monogenic patterns, meaning a single genetic variant largely controls whether or not people can smell the odour.

For example, the ability to smell β-ionone, which is found in rose oil and many different perfumes or colognes, is largely dictated by rs7943953. People who carry one or more ‘G’ can smell β-ionone, while those carrying a ‘T’ generally do not [5] Jump to reference section: [5] .

Another chemical that has wide variations amongst humans is Androstenone. This steroid is a sex hormone in a number of different mammalian species, and its smell is generally very unpleasant to humans. People who carry two G’s at rs5020278 typically experience a very unpleasant smell, while people who carry one or more A’s rs5020278 actually report a sweeter smell.

Finally, our body odors are also influenced by genetics. For example, the genetic variant rs17822931 in the gene ABC11, is strongly correlated with body odour. People who carry the TT genotype at this position have much less body odour - in one study these people were found to be 5 times less likely to need to wear deodorant! [6] Jump to reference section: [6] This SNP is not just linked to body odour, but also to ear-wax consistency [7] Jump to reference section: [7] . The SNP for crumbly ear wax and low body odour is found at much higher frequency in people with East Asian ancestry.

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Bottom line

Our sense of smell, as well as our bodies production of odours, are affected by many different genetic variants. This article highlights a number of well-studied examples, but we are clearly just scratching the surface. Only through greater research that we can fully understand the relationship between odour detection and genes.