Genetic diversity is particularly high within the olfactory receptor gene family. Although so-called “natural knockouts” mutations that make a gene non-functional are uncommon across the genome, they occur relatively frequently in olfactory receptors. On average, two individuals differ in the functioning of about 30% of their roughly 400 olfactory receptors.

Which means that each person perceives odors in a unique way. In this sense, just as everyone has distinct fingerprints, each individual also has a personal “nose print”

To demonstrate this concept, participants smell a set of odors and indicate whether they detect each one and whether they find it pleasant. Using scents commonly found in foods, drinks, and personal care products helps connect this genetic variation to everyday experience and highlights how it shapes our interaction with the environment.

• Beta-ionone has a characteristic violet-like scent. For about half of the people, it smells strongly floral; others perceive only a faint sweet note, while some cannot smell it at all.
  
  Because the population is split roughly 50/50, this odor alone can be used as a simplified version of the demonstration: some participants will smell a clear floral scent, while others will perceive almost nothing. Although less striking than a full panel, it still illustrates genetic effects on perception.
  
  Beta-ionone is commonly present in perfumes, as well as in foods and beverages such as pinot noir, raspberries, and mangoes. It is also found in violet essential oil. Sensitivity to this compound is associated with genetic variation in the receptor OR5A1.

• Guaiacol produces a smoky aroma typical of bacon, smoked fish, beef jerky, and peaty whisky. Guaiacol is also present in liquid smoke. Most people can detect it, but sensitivity varies considerably.
  
  Interestingly, perceived pleasantness tends to decrease as intensity increases; the stronger the smell appears, the less enjoyable it is. As a result, participants usually agree on detecting the odor but differ in how much they like it. This variation is linked to differences in the receptor OR10G4.