23andMe Review: Unzipping Your Genes

by Brian on July 30, 2013 in Genetics

[NOTE: This review is based on the pre-Nov. 22, 2013 version of 23andMe. The version of 23andMe made available after FDA approval in 2015 differs in some respects, but much of what I say here still applies.]

When big stories splash across the news like Angelina Jolie deciding to get a double mastectomy (i.e., cut off her breasts) as the result of a DNA test, it’s easy to start wondering what lurks in your genes and how it might affect you without you even knowing it.

Determining genetic disease risk, athletic potential, or digging into your ancestry are among many reasons you might opt for personal DNA testing.

Genetic tests used to be a luxury only the rich could afford, sometimes costing thousands of dollars. However, 23andMe has changed all that with an affordable personal DNA testing service that provides a breathtaking array of genetic data and lifetime updates as new research becomes available. All of which is conveniently available to you through an online account.

Crash course on DNA, SNPs, and genotyping

DNA is composed from a sequence of four different nucleobases represented by the letters G-C-A-T (guanine, cytosine, adenine, and thymine).

Your genome (the entire set of your DNA) contains 23 chromosomes, and your individual genes all live somewhere on one of those chromosomes. You have two full sets of chromosomes–one from your father and one from your mother. Which means that you also have two copies of each gene.

Using encyclopedias as an analogy, your genome is like a 23 volume set of encyclopedias. Each volume in the set is like one of your chromosomes. An entry in one of the volumes is like an individual gene. And a SNP (single-nucleotide polymorphism; pronounced “snip”) is like a single-letter spelling mistake in one of the entries. For example, one bit of DNA on a gene might read “GAGCT” where it should read “GAGAT.”

You inherited one set of “encyclopedias” from your mother, and one set from your father.

Genotyping looks at SNPs to see what “spelling mistakes” you have in your DNA, or which version of a gene you have. This is different from DNA “sequencing,” which is essentially just writing out your DNA in the alphabet of G-C-A-T.

The raw sequence of your DNA is not particularly helpful unless you know how to parse the data. What you are really interested in is if you carry a genotype known to be associated with a particular health condition. For example, BRCA1 and BRCA2 are the genes associated with high breast cancer risk. We all have BRCA1 and BRCA2 genes, but what you want to know is whether you have the “bad” version of them or not–even if you’re not a woman, you still have the potential to pass the high-risk variant to your daughters if you are a carrier.

Whereas many genotyping services cost hundreds of dollars and only test a handful or even single SNP, 23andMe is a genotyping service that currently looks at an industry leading 1,000,000 SNPs across your 23 pairs of chromosomes (including SNPs on the BRCA1 and BRCA2 genes).

Health Risk & Trait Reports

23andMe gives you reports on 240+ health conditions and traits and 40+ inherited conditions.

Health risk reports are conveniently organized inside your online account by conditions where you are at high risk, typical risk, or decreased risk. Some common conditions include:

  • Celiac disease (especially of interest for the nutrition conscious)
  • Heart disease
  • Bipolar disorder
  • Diabetes
  • Restless leg syndrome

You have to take the results in perspective though. While I’m genetically susceptible to Celiac and have 4.08x risk of the average person, 23andMe still reports my overall risk at only 0.48% for the condition (based on real life experience I probably have some degree of gluten sensitivity but not full blown Celiac).

In case you’d simply rather not know or can’t face your risk of certain extremely debilitating diseases, you have to agree to a consent form to view your results for these conditions:

  • Cancer (including the breast cancer genes)
  • Parkinson’s disease
  • Alzheimers

23andMe stresses that just having the genes for increased risk is not a guarantee that you absolutely will contract the condition, and you should consult a medical professional or counselor if you are at risk.

If you need medication or might be put on medication, 23andMe tells you what medications you might be sensitive to and should be careful about taking.

Other reports tell you about inherited conditions like your susceptibility to infectious diseases and physical traits. You might enjoy finding out how your genes stack up against these traits:

  • Norovirus resistance (a type of food poisoning)
  • Resistance to HIV/AIDS
  • Malaria resistance
  • Muscle performance (ACTN3, the so-called “sports performance gene”)

Sadly, I should be careful with the oh so tasty raw oysters because I don’t have the norovirus resistance gene variant.

On the lighter side, you can also learn about things like whether you have wet or dry earwax type and if you have the genes to smell asparagus pee.

Ancestry & Genealogy Reports

neanderthal

The Neanderthal Ancestry report has to be my favorite thing I got from 23andMe. If you are of European or Asian descent, you likely have 2-4% Neanderthal DNA. It turns out I have 3.2% Neanderthal DNA which puts me in the 99th percentile of all people 23andMe has tested.

On the more conventional side, the Ancestry Composition report gives you insight into your ethnic background based on 22 different worldwide populations. I must admit that if I felt disappointed about any part of the service, this was it, since nearly 90% of my ethnicity came back as a combination of “Nonspecific Northern European” and “Nonspecific European.”

ancestry

The test did, however, help me rule out speculation that there may have been some Cherokee blood on my dad’s side of the family. I have heard that National Geographic’s Geno 2.0 Ancestry Kit may provide more detailed ethnicity information, but I haven’t had a chance to check it out.

Maternal line and paternal line reports give you insight into the migratory routes your ancestors took by looking at your “haplogroup”–determined by genetic markers found on the Y chromosome (from your father) and mitochondrial DNA (from your mother).

I learned through the paternal line test that the Brookshire line originated on the west coast of England, most likely in the Lake District, as we had suspected. I discovered that my maternal line passed through India 45,000 years ago long enough to evolve some new mitochondrial DNA before moving on to become some of the first modern human inhabitants of Europe. Note that if you are a woman, you will have to get a brother or father to sign up to find out about your paternal haplogroup since you don’t have a Y chromosome.

If you are hardcore about genealogy and mapping your family tree, 23andMe shows you other members who may be your genetic relatives with a prediction of relatedness. You can contact them and opt to share your data and look for relatives in common.

Browsing raw data

If you really want to geek out on your DNA results you can browse through the raw data to find your genotype for any of the SNPs that 23andMe tests.

Even if 23andMe doesn’t have a report for a specific health condition, they may still have determined your genotype for the relevant SNPs. As a prolific reader of health and nutrition information I’ve used it to look up my type for conditions like hemochromatosis and MTHFR deficiency–either of which could have been a $150-200 test on its own through another testing service.

Odds are if you come across mentions of a genetic condition on the news or a blog, you can consult SNPedia to find the relevant SNPs or find someone who has posted on 23andMe’s online community with links to the SNPs and what variants to look for.

You can even extend analysis of your 23andMe raw data by using 3rd party services like Genetic Genie.

The Bottom Line

I have already spent hours and hours digging through health information, learning about my ancestry, and reading the highly informative forums–which often contain posts by professional geneticists. I still continue to use 23andMe to look up my genotype for SNPs when I read about new genetic conditions.

If your doctor has ever recommended you get tested for a genetic condition, you may want to find out if 23andMe reports on it first because you will get that data and so much more with it–most likely at a significantly lower price to boot.

In the current market, full genome sequencing will still cost you a cool $7,000 and many services charge $200-$300 to only test a handful or even a single SNP (single letter gene variant).

23andMe’s personal DNA genetic testing for health, disease, and ancestry service provides you with reporting on 1,000,000 SNPs for the astoundingly low price of only $99. The usefulness of 23andMe skews slightly more towards the health side than the ancestry side, but you simply will not find more bang for the buck anywhere else.

If you are interested in ordering a 23andMe DNA test kit, you can buy them here.

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{ 6 comments… read them below or add one }

Allison Peacock July 31, 2013 at 5:18 pm

This is the second or third time one of your blog posts has mirrored something going on for me, too. I was just tested by 23andme for a casting call on PBS’s new Genealogy Roadshow. I was also disappointed in the ancestry side, but thought the health results were interesting. The broad and general nature of most of the data might not make it highly usable for practical purposes but it’s sure interesting. I learned a lot from your post that makes understanding my report easier. Thanks for breaking it down!

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Allison Peacock July 31, 2013 at 5:26 pm

Oops, I totally forgot what made me chuckle about the similarity in experiences. It was the Cherokee thing. My aunts have proclaimed for years that my grandfather’s grandmother was Cherokee, yet I couldn’t find it in several years of serious genealogy study. So it was really gratifying once and for all to send them my DNA results that I am 99.7% European. (There was that drop of Neanderthal, like most all of us have.) Otherwise as I told my Facebook friends I’m “just plain old white girl.” No more perpetuating false family history. DNA doesn’t lie. 🙂

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Brian July 31, 2013 at 6:44 pm

Hah, funny. Interesting to know I’m not the only one running around with rumors of Cherokee in the family. It’s nice that we can finally put these things to rest with DNA. I’ll probably try out National Geographic’s Geno 2.0 test sometime and see if it can give me more insight into the “Nonspecific European.”

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D. Baker April 21, 2015 at 12:31 am

I just received my results from 23andMe a few weeks ago. My parents and a maternal grandmother had been tested through the company last year, so I was able to compare my “Ancestry Composition” with them. Apparently, Italian and North African ancestry skips a generation. I also didn’t get any of the Native American that my dad has. After they matched my family to me, they also reduced my British/Irish from 47.1% down to 37% and jacked up my dad’s from 18% to 41%.

Needless to say, I sure wouldn’t dismiss any genealogical research on account of 23andMe’s Ancestry Composition results.

Did you get around to doing the National Geographic Geno test? If so, did the results seem better than 23andMe?

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Brian April 21, 2015 at 1:19 am

The Geno 2.0 test is interesting in its own way, but it only looks at paternal line traced through Y-chromosome and maternal line traced through mtDNA.

I’ve had multiple tests done with myself and relatives on 23andMe, AncestryDNA, and Family Tree DNA. I’m still not particularly impressed by the ethnicity reporting for any of them, although it has improved somewhat as companies have expanded their databases and improved their matching algorithms. All 3 of those services now report roughly the same composition for me.

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Lisa Manon (Brookshire) September 21, 2016 at 4:52 pm

Brian,
My new Neanderthal variant count is 328.
Since you and I are 3rd cousins I now KNOW my cool cave-man genes are from my paternal lineage.

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