Bitter Taste Sensitivity
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Do you love or hate Brussels sprouts? People have different levels of sensitivity to bitter tastes, so our like or dislike of bitter foods is at least partially genetic. And based on your DNA, an AncestryDNA® test can estimate how sensitive you are to the bitter tastes associated with certain vegetables.
Bitter Taste and PTC
Vegetables like Brussels sprouts, kale, and cauliflower all contain a group of natural chemicals called glucosinolates. These compounds can taste bitter to some people—but not to everyone. That some people are able to taste bitterness but others are not was discovered back in 1931. A chemist named Arthur Fox was pouring a synthetic powdered chemical called Phenylthiocarbamide (or PTC, a chemical similar to glucosinolates) into a bottle. Some of the powder went into the air, and one of his colleagues complained the PTC dust had a bitter taste. Fox tasted nothing. A few experiments later, he realized that people are either "tasters" or "non-tasters" of PTC.
The Inheritance of Bitter Taste Perception
Sensitivity to bitter taste is a dominant trait. That means if both of your parents can't taste PTC, you're also likely to be unable to detect PTC's bitterness. If you were all to take a PTC test (which you can do by placing a strip of special PTC-laced paper on your tongues), you would all be "non-tasters." If, on the other hand, at least one of your parents is a taster, you might have a range of sensitivity. This could vary from not tasting PTC at all, to finding it a bit disgusting, to finding it quite repugnant. When you get a range in a trait like this, the trait's inheritance is described as “incomplete dominance.”
The Genetics Behind Bitter Taste Perception
The TAS2R38 gene is the one that determines how sensitive you are to the bitter tastes associated with PTC or glucosinolates. It encodes the protein that controls your ability to detect these bitter-tasting compounds and is sometimes called the PTC gene. AncestryDNA looks at three well-studied markers in the TAS2R38 gene where the gene exists as one of two possible variants—the "taster" variant and the "non-taster" variant. You could have variations of the TAS2R38 gene linked to non-tasting, to tasting, or to one of each. And it's these variations of the TAS2R38 gene that determine how sensitive you are to the glucosinolate compounds that can make some foods taste bitter.
Fun Facts About PTC
Since the "taster" or "non-taster" status is inherited and is relatively easy to test (even babies can make faces when something's bitter), PTC was used for paternity testing in the days before DNA testing.
While the PTC gene does have a significant influence over whether someone is a "non-taster" or a "taster," there are other factors that impact your ability to taste PTC, such as a dry mouth (which can make it harder to taste the bitterness of PTC).
Interestingly, there are chimpanzees that are also “non-tasters.” But they have different genetic variants that lead to their being “non-tasters”: unlike non-tasting humans, non-tasting chimpanzees appear to be missing functional PTC receptors.