Exploring my genome with 23andMe - traits

This is the third in my series of articles on my experiences of testing with 23andMe. I wrote yesterday about my carrier status and drug responses, and on Monday I discussed my disease risks. I'm now going to look at my results for the various traits. The 23andMe test currently covers 40 traits from the mundane, such as eye colour, hair curl and height, to the obscure such as "asparagus metabolite detection" (the ability to detect a distinct smell in your urine after eating asparagus). The screenshot below shows a selection of my results. (Click on the screenshot to enlarge it.)

One of the useful aspects of the data on traits is that you have the opportunity to see how your genetic predictions match the reality. According to my genotype I have a 72% chance of having blue eyes, a 27% chance of having green eyes and a mere 1% chance of having brown eyes. My eyes are actually green so the prediction is accurate, but this is also a useful reminder that the most probable prediction is not necessarily the reality.

For many of the traits 23andMe provides reports on more than one marker. The results can often be contradictory, again reflecting the complex pattern of genetic inheritance. There are for instance two reports on hair curl.  The confirmed research report suggests that I should have "slightly curlier hair on average" whereas according to the preliminary research report I am predicted to have only a typical amount of hair curl. In reality I have a mop of thick curly hair. The reports do explain that "this biological trait has a strong genetic component, although a simply inherited 'hair curl gene' that completely determines hair texture has not been found and likely does not exist. Instead, variations in several genes affecting different aspects of hair development probably combine together to determine the shape of your 'do". (I've never heard the expression 'do before but I presume it is perhaps an abbreviation for hairdo.) My sons have both inherited my thick curly hair so there is a strong possibility that they will also have inherited my marker for male pattern baldness. According to the preliminary report: "Sons of women with this genotype have a 50% chance of inheriting greatly decreased odds of male pattern baldness."

As another example, 23andMe provides preliminary reports on two markers for longevity. I have one marker which gives me higher odds of living to 100 and another marker which gives me typical odds of living to 95. The reported studies were however both very small – a study of 212 Ashkenazi Jews and a study of 615 Japanese men.

I have never been particularly athletic so it is no surprise to learn that I do not have "fast-twitch muscle fibre" and am therefore unlikely to be a fast sprinter. I didn't really need a DNA test to tell me that I have wet earwax, but on reading the report I now have a new word cerumen - the technical term for earwax - to add to my vocabulary!

One of the most interesting findings in my traits reports was the discovery that I have a genotype which makes me resistant to the most common strain of norovirus. Apparently because I have two As on this particular SNP I lack a functioning FUT2 gene. I was fascinated to learn that about 20% of people with European or African ancestry, but very few people with Asian ancestry, share this trait. I'm not however in any great hurry to go on a cruise to test my resistance!

The most innovative feature of the 23andMe service is that customers are given the opportunity to participate in the company's research programme, 23andWe. The company's first scientific paper, Web-Based, Participant-Driven Studies Yield Novel Genetic Associations for Common Traits, was published in June this year in the open-access peer-reviewed journal PLoS Genetics. The data on some of the traits on which the company reports, such as "photic sneeze reaction" and the above-mentioned asparagus metabolite detection, are taken from this paper. While the traits are somewhat trivial and insignificant, the open web-based research model has been validated and there will no doubt be many interesting discoveries in years to come. It is very exciting to be able to engage with your data in such a way and to have the opportunity to find out how your results compare with those of other participants and to see how your data has been used.

One of the best features of the test is the interactive nature of the website and the fact that your results are constantly updated. I've already had a number of new results in the last few weeks, the most recent of which was for leprosy susceptibility. Not all of the information will necessarily have any practical application. I am highly unlikely ever to contract leprosy and probably many of the other diseases for which I have reports. However, new studies are being reported every week and the value of the test will grow over time. Although I was primarily motivated to purchase a 23andMe test for the ancestry aspects I have found the medical aspects very interesting and educational. There is no better way to understand genetics than to have the opportunity to explore your own genome.

See also

Part 1 Disease risks

Part 2 Carrier status and drug responses

Part 4 Ancestry

© Debbie Kennett 2010