Since I received the results from my direct-to-consumer (DTC) DNA spit kit last February, in addition to my original report, close to 20 emails have landed in my inbox. They invite me to take part in new research projects or examine updated reports for such non-health-related traits as the likelihood for my hair to lighten after being in the sun, called photo bleaching. (My report notes that my hair is more prone to lighten, which is true.)
Much the same as last year, many of these kits may be finding their way under the Christmas tree or into holiday stockings next week.
The overwhelming draw of DTC genetic kits is their appeal to discover more about one’s ancestry and heritage, as well as health and wellness. When I first wrote on this topic, I sought details about my risk for heart disease, given my family history, but as I learned from speaking with several Penn Medicine geneticists, DTC kits aren’t set up for this area yet. However, it is possible to glean the genetic basis for seemingly off-beat behaviors and traits, such as toe-length ratio or sweet-versus-salty taste preference. My report states that I should have a longer big toe (true) and “likely prefers salty” (Nope, I adore salty foods as much as sweet foods).
Even well-known science writers are part of the legions of citizen DNA science participants. Earlier this year, Tina Hesman Saey from Science News wrote about her experience comparing three types of personal DNA sequencing tests. Saey, trained as a molecular biologist, explains the basis of the tests and the nature of genetic variation in humans: “These companies all analyze natural spelling variations in the string of letters that make up DNA. Where most people have, say, a ’G,’ some might have an ’A.’ Most of these genetic variants are harmless, but some raise the risk for certain diseases.”
These small variations are what make us all different and now, perhaps more eager to part with $100 to find out how much coffee we are likely to drink or if we might grow a unibrow – “more likely,” and “no,” respectively, for myself.
Last June, the DTC firm I used added four new reports including wake-up time, aversion to cilantro, and getting irritated at the sound of someone chewing their food (known as misophonia). Not too surprisingly, wake-up time captured the interest of the popular science press, with articles in Shape and Wired earlier this year.
This exercise is all well and good, but I wondered whether the genetic reports on behavioral traits are meaningful or merely amusing? I asked Maja Bucan, PhD, a professor of Genetics and fellow DTC genetics subscriber, this question. She agreed there is no simple answer.
She notes that these companies ask a lot of questions in their qualitative surveys to give environmental context to individuals’ DNA, and when they get an answer, in many cases, it’s statistically significant because they have a large number of subscribers – in the millions.
“Many of these questions are asked for fun, but their analysis may show that some of these are linked to important health-related traits,” Bucan said. For example, the ability to taste bitterness. Scientists have long suggested that animals have developed this trait to help detect toxins or poisons in food.
Bucan’s trait results were also mixed. “My result shows that the average wake-up time for people with my genetic make-up is 6:57 a.m., but I need an alarm clock if I have to wake up by 7:00 a.m., and my wake-up time on weekends is 9:00 a.m.” Her results also reported that she was not fearful of heights. Not true, she says: “I hate steep paths and feel uncomfortable when high up, even on the roof of my one level house.”
I posed the same question about the utility of the traits data to Reed Pyeritz, MD PhD, a professor of Translational Medicine and Human Genetics, who was circumspect: “We'll see, eventually, to what extent behavioral traits, including even blatant ones, have a genetic basis, but it is premature now.” Nevertheless, he noted that my report contained more traits compared to his from more than a decade ago, when the DTC kits were just coming on the market.
There’s more in the literature now to data mine for associations. For example, ring-finger length. Yet, this trait is still confusing, in my case, according to Pyeritz, who looked over my report: “There are nine associations in you” — 7 plus and 2 minus for a longer ring finger compared to index finger, but the scientific report mentions 15 variants. He says that “this is clearly a multifactorial trait
For Pyeritz, the trait of mosquito bite frequency is the most perplexing. “Who can know for sure whether they get more bites than the next person?” he asked. To him, the accuracy of this phenotype is “markedly suspect,” making any genetic association with it “useless.” My report stated: “Likely bitten as often as others.”
As Bucan and Pyeritz have alluded, having a genetic predisposition to one trait or another does not mean that you will display that trait. Most characteristics, from heart disease to male pattern baldness, are shaped by many factors. The theme running through these confounding results is that most human characteristics are polygenic, meaning they are influenced by multiple genes — and numerous variants within those genes — versus other characteristics such as blood type that exert a yes-or-no genetic influence.
It seems the answers to whether behavioral trait genetic reports are of any consequence or simply to confirm what we already know or believe, are just as complicated as human genetics itself. No easy yes or no answer here. However, one thing is for certain, I will be looking forward to the next update from my perpetual genetic present.