Understanding DNA Traits Reports

Your results tell you the version of each trait you are most likely to have based on your genetics (and, depending on the report, sometimes also based on your age, sex, and/or ethnicity).

It's important to remember that being more likely to have one trait than another doesn't mean you will definitely have that trait. So your results also show your chances of having the trait by illustrating 100 23andMe research participants with genetic results (and, depending on the report, other factors like age, sex, and/or ethnicity) similar to yours:

Taking the Earwax Type Report as an example: out of 100 23andMe research participants with genetics like Becca's, 93 have wet earwax, while 7 have dry earwax.

You can also learn from this image that Becca has a 93% chance of having wet earwax. Since this likelihood is greater than 50%, that's the outcome we predict for Becca.

At the same time, this image also shows that Becca has a 7% chance of having dry earwax — less likely than wet earwax, but still possible. So what would it mean if Becca actually had dry earwax? She would fall in that smaller group, the 7% of people with her genetics who buck the trend.

Learn more about how your likelihood of having or not having a trait is estimated

Most people will have at least one prediction that they are likely to have a trait they don't actually have. Taking Becca for example again, 7% of people with Becca's genetics actually do have dry earwax, even though our report would say they are more likely to have wet earwax.

That's because genetics aren't destiny. Your genetics are almost never the only factor that shapes your traits. Predictions based on your genetics will be statistical, or probabilistic — genetics can provide likelihoods, but not certainties.

For example, the Earwax Type Report is based on a single genetic marker that has a strong impact on earwax type. Knowing about your genetics at this marker allows us to make a statistical prediction about the chances that you have wet or dry earwax.

But there could be other genetic factors scientists don't yet know about that influence earwax type. There could also be non-genetic factors at play, such as your age, environment, or lifestyle.

If you're one of these exceptions to the rule — someone who has a different trait than what your genetics would suggest — consider whether one of these other factors could have pushed your development in the opposite direction.

Traits Reports can work in one of two ways, depending on how many genetic markers the report is based on

• One or a few genetic markers:

  These reports are based on what we call a "curated model". We identified published scientific literature supporting an association between a particular genetic marker and a trait. The version of DNA you have at that genetic marker (your genotype) can impact which version of the trait you are more likely to have. In some cases, like the Red Hair Report, we test your genotype at multiple genetic markers that have been identified in the scientific literature.

• Many genetic markers:

  These reports are based on what we call a "statistical model". Most of your characteristics are influenced by your DNA at many genetic markers. Each individual genetic marker has a small impact on your overall chances. Statistical models combine the effects of your genetic variants at multiple genetic markers, plus the effects of other factors including age, sex, and/or ethnicity, to calculate your result.

You can learn more about the genetics of your Traits results in the section of each report titled "How did we calculate your result?" and on the Scientific Details page of the report.

Trait inheritance: beyond recessive and dominant traits

You may remember learning way back in biology class that some traits have "dominant" and "recessive" versions: you need to have two copies of the recessive variant to display the recessive version of the trait, but you need just one copy of the dominant variant to display the dominant version of the trait. This pattern of genetic inheritance is known as Mendelian inheritance. Eye color is often used as an example, with blue eyes being recessive and brown eyes being dominant.

People sometimes want to know whether they can trace the inheritance of dominant and recessive traits and genetic variants in their family. A lot of the time, though, things aren't really that simple! This is because most traits aren't passed down in a strictly Mendelian fashion (that is, with dominant and recessive versions of one gene determining the trait). Here are some of the ways trait inheritance isn't always truly Mendelian:

• Traits aren't always completely dominant or recessive. To continue with the example of eye color, brown eye color isn't perfectly dominant, meaning that if you have one or two copies of the "brown eyes" variant (a genotype of AG or AA at the marker in the Eye Color Report), you are more likely to have developed brown eyes than blue — but you still had a chance of ending up with blue eyes. Similarly, even if you have two copies of the "blue eyes" variant (a genotype of GG at this marker), there is a small but real chance that your eyes turned out brown.
• There can be more than two versions of a trait. In the case of eye color, eye color varies from blue, to green, to hazel, to brown. Green and hazel eyes are neither recessive nor dominant phenotypes, but somewhere in between. (There are also gray eyes, though scientists are less sure what makes eyes gray — but that's another story.)
• Traits can be influenced by many genetic markers, some of which may not yet have been identified. Many traits that were originally thought to be determined by a single gene passed down in a Mendelian fashion, like cleft chins and earlobe type, have since been found to be influenced by many genetic markers. As the field of genetics grows, we continue to learn more about the many ways our genes influence our phenotypes.

First, we identified genetic variants that occur more often in people with a certain version of a trait. For some traits (the ones based on statistical models) we did this using data from thousands of 23andMe research participants, while others are based on research that has already been published by other scientists (curated models) and supplemented by data from 23andMe research participants.

Then we look to see if you have those genetic variants. Based on your genetics, and sometimes your age, sex, and/or ethnicity, we create your personal Traits predictions. These predictions give the chances of someone with your genetic profile, age, and/or sex having a particular trait.

We created the Traits Reports using data from 23andMe research participants, and we did not have as much data from participants of non-European ethnicities. That means these reports may be less accurate for people of non-European ethnicities. In the future, we will keep looking for ways to improve the accuracy of Traits Reports for more ethnicities.

For some Traits Reports, we can take into account your self-reported ethnicity to improve trait predictions for people of certain ethnicities. You can review or change your ethnicity information in Settings at any time.

With your Traits Reports you can explore what your genetics say about your appearance and senses, but also learn that some people defy the odds. This is an important lesson to keep in mind as you read your other reports, but there are also some important differences from other report categories.

Traits Reports vs Wellness Reports

Wellness Reports are similar to Traits Reports, but focus on topics that relate to lifestyle, like sleep, diet, and exercise.

Traits Reports vs Health Predisposition* and Carrier Status** Reports

• Traits Reports can be based on 23andMe internal research or the published scientific literature, while Health Predisposition (including Genetic Health Risk) and Carrier Status Reports are all based on the published scientific literature.
• Traits Reports are based on genetic variants that are statistically associated with certain traits. Scientists don't always know whether these variants influence the trait directly or indirectly. Health Predisposition and Carrier Status Reports are based on specific genetic variants with strong evidence that they directly influence disease risk or cause the disease
• Because of differences in the available evidence for each category of reports, we have slightly different standards for scientific and clinical validity for these categories. See our white paper on scientific standards for our Health and Traits Reports.

We created the Traits and Wellness Reports with the help of data from 23andMe research participants. Using these data, we were able to discover brand-new genetics behind traits like hair texture, cleft chins, sweet vs. salty taste preference, and more!

You can help us in our effort to create new reports and improve existing models by consenting to participate in research, and then answering research questions.

• To view or change your research consent, go to Settings > Preferences > Research.
• To answer research questions, go to Research > Questions.