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A study published in March in the journal <a href="http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0032840">PLoS ONE</a> suggests that having more African ancestry is associated with higher risk for type 2 diabetes.
Type 2 diabetes is one of the most common chronic diseases in the United States, affecting about 26 million people and more than 25% of the population over the age of 65. While most people realize that lifestyle factors like an unhealthy diet and lack of exercise increase the risk of developing the disease, many may not realize that ancestry plays a role, too. In fact, type 2 diabetes strikes non-white ethnic groups at higher rates, with African Americans experiencing the highest rates of all. 
 
Higher rates of obesity and heart disease, and lower socioeconomic status in the African American population certainly contribute to this trend, but, as <a href="http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0032840">this study</a> found, those factors aren’t the whole story. Led by Ching-Yu Cheng and Linda Kao from Johns Hopkins University, the research team analyzed DNA from more than 7,000 African Americans and found that those with the most (&gt; 87.5%) African ancestry had about 33% higher odds of type 2 diabetes compared to those with the least (&lt; 80.5%) African ancestry after accounting for body mass index (BMI) and socioeconomic status.
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See your <a href="https://www.23andme.com/you/ancestry">ancestry breakdown</a> in your 23andMe account.
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A person’s ancestry can be traced back to various regions of the world (e.g., Europe, Asia, and Africa) using genetic markers that are known to be indicative of those ancestral groups. On average, the African Americans in the study had about 84% African ancestry.
Cheng and Kao’s findings add further support to the idea that differences in disease rates across different populations can be partly explained by ancestry genetics. A previous study looking at <a href="https://blog.23andme.com/articles/the-ancestry-link-for-atrial-fibrillation-risk">atrial fibrillation (a heart rhythm disorder) in African Americans</a> also found that having more African ancestry correlated with higher odds of the condition. Most likely, correlations like these reflect variations in the frequency of many different genetic factors involved in disease. In a few cases, though, individual genetic factors can have greater importance. For example, in East Asians, who have some of the highest rates of esophageal cancer in the world, a specific genetic factor causing the “<a href="https://blog.23andme.com/articles/researchers-warn-that-physicians-need-to-ask-about-alcohol-flushing-to-reduce-esophageal-cancer-risk">alcohol flush</a>” reaction plays a direct role in the development of esophageal cancer.
Studies like this one highlight the complex interplay between ancestry and health in African Americans, the vast majority of whom can trace significant parts of their ancestry back to at least two continents. Combined with <a href="https://www.23andme.com/ancestry/recent/">DNA-based tools</a> that allow people to see their <a href="https://www.23andme.com/dna-ancestry/">ancestral breakdown</a>, health risk assessments that incorporate genetic ancestry may help make healthcare more personalized.

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African Ancestry and Risk for Type 2 Diabetes

For back-to-school month we’re running a series of posts on genetic factors that may impact learning. Here we describe a variant that may influence a person’s ability to learn from their mistakes. In a <a href="https://blog.23andme.com/traits-2/back-to-school-smarts-and-genetics/">prior post</a> we discuss a variant linked to non-verbal IQ performance.
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</a>Attribution: http://xkcd.com/242/
Why do some people have a hard time learning from their mistakes?
It might have to do with genetics. At least one research study suggests that the tendency to make rewarded choices while avoiding those that receive negative feedback may be influenced by genetics.
In <a href="https://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Search&amp;db=pubmed&amp;term=18063800">this study</a>, 26 German individuals took a test that assessed their ability to prefer &#8220;correct&#8221; choices and avoid &#8220;incorrect&#8221; ones. The authors genotyped the subjects at the SNP , which is thought to affect a gene involved in dopamine signaling. The neurotransmitter dopamine is involved in trial-and-error learning and variations in genes related to dopamine signaling may also affect a person&#8217;s ability to learn.
People with the GG genotype at learned to avoid choices associated with negative feedback relatively easily, while people with the AG or AA genotypes did not learn as well to avoid these &#8220;punished&#8221; choices; in other words, they did not learn from their mistakes. The AG and AA genotypes have also been correlated with up to a 30% reduction in dopamine receptor density in a region of the brain known as the striatum.
( is commonly referred to in the scientific literature as the DRD2 TaqIA polymorphism. The A version of is equivalent to the A1 allele of DRD2 TaqIA, while the G version of the SNP corresponds to the A2 allele.)
 
If you’re looking for a genetic excuse, this is a good one to point to. The next time your spouse is amazed that you left the house again without your phone … or house keys … just say that you’re genetically predisposed to not learn from your mistakes.
The results presented here were obtained with a very small sample size and have not been independently replicated. While the results are intriguing, it’s important to realize that learning is an extremely complex behavior that is also strongly influenced by environment.
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Genetic Differences in Dopamine Receptors and Effect on the Brain 

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In a more recent <a href="http://www.jneurosci.org/content/29/12/3695.long">study</a> by the same researchers, 28 German males performed a similar learning task except partway through the experiment the “correct” choice was reversed – the one that used to be right was now wrong. The scientists found that people with at least one A at had a hard time consistently choosing the “correct” response after the reversal even if they had just chosen and been rewarded for that response. Perhaps not surprisingly, the behavior seemed to correlate with differences in brain activity. The researchers imaged the participants’ brains (with <a href="https://en.wikipedia.org/wiki/Functional_magnetic_resonance_imaging">functional magnetic resonance imaging, or fMRI</a>) while they performed the task and saw more signal in GG individuals (A1- in the figure) compared to AG and AA people (A1+ in the figure) in parts of the striatum and ventral midbrain where dopamine receptors are located. A similar correlation between reduced brain activity in dompinergic regions of the brain and impaired ability to “learn from mistakes” was also observed in the original study. Figure from: <a href="https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&amp;retmode=ref&amp;cmd=prlinks&amp;id=19321766">J Neurosci. 2009 March 25; 29(12): 3695—3704. </a>
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Back-to-School: The Genetics of Learning from Your Mistakes

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Editor&#8217;s note: The post has been edited from the original to reflect changes in the product.
We’re a little late to the party, but yesterday a consortium of scientists, who are part of a project called The Encyclopedia of DNA Elements, or<a href="https://www.genome.gov/10005107"> ENCODE</a>, came out with what some are calling a roadmap of the human genome.
<a href="https://www.nature.com/nature/journal/v489/n7414/full/489049a.html">It’s a big party.</a>
More than 400 scientists worked on the project, which was funded by the National Institutes of Health over the last five years at a cost of about $130 million. The announcement came with a blizzard of 30 papers in the journals Nature and Genome Research and many more are expected to come.
There has been some great coverage that explains both the background and gives some context, such as a nice piece by Nature writer<a href="https://www.nature.com/news/encode-the-human-encyclopaedia-1.11312"> Brendan Maher’s</a>. Discovery Magazine blogger Ed Yong did a yeoman’s job of the history of ENCODE’s work and what the future may hold. And <a href="https://www.nytimes.com/2012/09/06/science/far-from-junk-dna-dark-matter-proves-crucial-to-health.html?_r=2&amp;hp">Gina Kolata’s article</a> in the New York Times includes our favorite quote. It came from Eric Lander, president of the Broad Institute, who compared the data to a sort of Google Map of the genome and said it was a stunning resource for researchers.
“My head explodes at the amount of data,” Lander said. 
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Us too, and the challenge is really giving people a sense of what it all means. Much of the work in genetics has been focused on the areas in our DNA that code for proteins, but this is a very small part – just 1 percent – of our genome. The ENCODE project is an attempt to map the other 99 percent, the uncharted “dark matter” of our genome.
There’s much that’s interesting there it turns out. And the work sheds some light on the importance of what once was labeled “junk DNA.” It turns out, unsurprisingly, that it’s not junk and the data from ENCODE provides evidence that many of those mysterious regions of the genome play important functional roles.
For us at 23andMe the <a href="http://regulomedb.org/">ENCODE data</a> sheds more light on some of the genetic variations (mainly single nucleotide polymorphisms, or SNPs) scientists have associated with health conditions and traits. S
There are many SNPs in the 9p21 region associated with coronary heart disease, and based on the ENCODE data, it appears that this SNP and rs1333047 are the primary functional SNPs. Of the various SNPs in the region, <a href="https://genome.cshlp.org/content/22/9/1748.full">rs10757278 and rs1333047 are likely to affect the binding of transcription factors</a>  – proteins that bind to DNA and regulate the expression of genes. These two SNPs are perfectly correlated in people with European ancestry, and the G version of rs10757278 is associated with higher odds of coronary heart disease in people with European ancestry.
Another example is the SNP rs964184 located near the APOA5 gene, which has also been associated with cholesterol levels. The ENCODE data show that it likely affects binding of transcription factors and results in differences in expression of a &#8220;target&#8221; gene of those transcription factors. The G version of rs964184 is associated with higher odds of coronary heart disease in Europeans.
These examples highlight how this new data can inform the “why” and “how” of genetic associations. Where before scientists often had very little idea which exact SNP was involved and why it was associated with a disease, now we can narrow down the SNPs likely to be responsible and start looking at their biological impact. The ENCODE data show what Kolata describes as at least four million gene switches in our DNA that collectively control how the cells, organs and other tissues in our bodies develop and behave.
Though there’s still much to learn about this newly revealed and incredibly complex genetic circuitry, it’s clear that the data will be a resource for many scientists working in genetics including us here at 23andMe.

A Map of the Uncharted Genome

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Editor&#8217;s note: This post has been edited from the original to reflect changes in our product.
If you want to stir up trouble, start talking about genetics&#8217; role in intelligence.
First, there’s the question of what you’re talking about: Is intelligence measured through mathematical skills, problem-solving, perceiving emotions, or a raw score from an I.Q. test?
<h2>Complex Traits</h2>
Not to be glib, but understanding intelligence – how to measure, define, and figure out what can influence it – takes some brainpower. It’s complicated. Innumerable factors influence intelligence – a layered mix of biology and environment. Access to education, your economic well-being, and even the prevalence of parasites in your community impact IQ scores.
That said, there’s good evidence that some differences in measurable intelligence, such as your IQ score, can be chalked up to genetics. While IQ tests don’t consider essential life skills – things like your powers of persuasion or your ability to build consensus and feel empathy – the tests are valuable nonetheless. At the very least, your IQ score is a pretty good predictor for how well you’ll do in school.
<h2>IQ Score Not Always the Right Measure</h2>
As Richard Haier of the University of California at Irvine said to Carl Zimmer in a Scientific American article, IQ score doesn’t tell you everything about how smart someone is.
But it’s like many other measurements that can be useful in the right context.
“When you see your doctor, what’s the first thing that happens? Somebody takes your blood pressure and temperature,” Haier said. “So you get two numbers. No one would say blood pressure and temperature summarize everything about your health, but they are key numbers.”
So, as we begin a series of “Back to School” posts, we’re going to take a moment to look at the genetics surrounding this one measure of intelligence. By the way, there will be a test—actually, three of them—in this series of posts.
<h2>Genetic Factors</h2>
As for measures of intelligence, recent studies estimate that in early childhood about 25-to-40 percent of individual variation in measurable intelligence can be attributed to genetics. In adults, this number increases to about 80 percent.
A study of Dutch families found that the SNP is associated with &#8220;performance IQ&#8221; (i.e., nonverbal IQ). Each A at increased subjects&#8217; performance IQ by an average of three points compared to those with no copies. The authors estimated that this accounts for 3.4% of the variation in performance IQ between people.
While the association between differences in IQ scores is significant, its overall effect is minimal, a difference of just three points on average.
It’s also important to note that no single gene has an inordinate impact on IQ scores. Instead, hundreds of genes impact intelligence with a cumulative impact on IQ scores. In a recent study, researchers <a href="https://www.ncbi.nlm.nih.gov/pubmed/22504419" target="_blank" rel="noopener">found</a> another variant, this one in the HMGA2 gene, that also has a small effect on IQ scores.
Although the HMGA2 gene has been associated with height, it also influences the size of the brain. Researchers also found that the C version of was also associated with a very slight increase in IQ. We wrote about this in the <a href="https://blog.23andme.com/articles/head-size" target="_blank" rel="noopener">Blog in April. </a>

Back to School Smarts and Genetics

<img loading="lazy" decoding="async" class="alignright size-medium wp-image-15308" title="HighlightedGraph" alt="" src="https://blog-api.23andme.com/wp-content/uploads/2012/08/HighlightedGraph-300x298.jpg" width="300" height="298" />Click on the image above for the interactive visualization.
Some things just go together – peanut butter and jelly, cheese and crackers, <a href="https://en.wikipedia.org/wiki/Tango_%26_Cash" target="_blank" rel="noopener noreferrer">Tango and Cash</a>. Other things not so much, or, at least, not until you dig into the connections a little deeper.
In health, the connection between two or more <a href="https://www.23andme.com/dna-health-ancestry/">health conditions</a> is often intuitive. If you grind your teeth, it stands to reason that you would have pain symptoms around the jaw. It makes sense that a person who has eczema might also have other skin conditions like dandruff or psoriasis.
But the connection between other health conditions isn’t always so obvious. Digging into those connections, finding out if they are real, and, if they are real, why they might be related, can tell us a lot of about disease.
With that in mind, we’ve created a visualization of several dozen self-reported health conditions from more than 38,000 members of CureTogether, which<a href="../news/curetogether-with-23andme/" target="_blank" rel="noopener noreferrer"> 23andMe acquired in early July</a>. CureTogether is a free resource for people to share information about diseases and treatments. This kind of data can be helpful to both members interested in comparing their own health issues with others, and researchers looking for a deeper understanding of illnesses.
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“(It) can give insights into the underlying biology of the conditions,” said Emily Chang, a scientist on 23andMe’s Science Content and Curation Team. “Perhaps there are genetic factors or environmental factors that predispose a person to both conditions.”
One condition might be a symptom of the other, but whatever the connection, exploring why two or more conditions might be related is essential.
“Accurate knowledge of a condition&#8217;s symptoms can aid biological understanding and improve diagnosis,” Emily said.
Daniel Reda, CureTogether’s co-founder and now a 23andMe Senior Product Manager worked with Emily to create the visualization. The two compiled more than 4.4 million points of data to show conditions and symptoms that have a statistically strong connection to each other.
“As we accumulate more data, we can replicate this type of analysis and this should help reveal which of the associations may be spurious and which are probably real,” said Daniel.
What Daniel and Emily have created is a sort of Wheel of Conditions. It shows connections between different conditions, diseases, and symptoms. Selecting a condition will highlight other conditions that are most likely to occur in common.
What you’ll see very quickly is that some of the connections, as we’ve said, just go together. Others, at first blush, may make you scratch your head, but digging a little may help explain the connection.
For example, why would anemia have a connection with infertility?
“(It) makes intuitive sense to me from an evolutionary perspective,” said Daniel. “The body would want to avoid the huge energy investment of pregnancy if the blood has potentially insufficient oxygen-carrying capacity. In ancestral times, vitamin deficiency from food scarcity would have caused anemia, so it would make sense for the body to be able to turn off its reproductive potential until conditions improved.”
The wheel also shows some conditions, fibromyalgia, for instance, are hubs for many others.
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Emily suggests that in some cases a condition may have a broad range of symptoms – pain, depression or fatigue – accounting for multiple connections.
“A large number of causes, the large number of symptoms and the difficulty in accurately diagnosing the conditions probably all contribute to many connections between these conditions and others on the chart,” she said.
What’s exciting is that this is just a first step. Integrating 23andMe’s genotypic and phenotypic data may be able to reveal a deeper understanding of the causes of these conditions.
“Hopefully, (it will) lead to more insights,” Emily said. “With a larger database we will be able to be more accurate making connections and also will be able to make more connections. Genotypic information can add still more.”
Combining genetic and phenotype data from these two large data promises to bring new understanding to disease.

Crowdsourcing Health Conditions

You may not think very much about yaks, but Tibetans do.
The domestic yak is crucial for their survival on the harsh Qinghai-Tibetan Plateau. The yak provides meat, milk and, to the distate of many Western travelers, salty yak-butter tea.  Like the people who domesticated it, the yak is tough, thriving at altitudes and with nutritional restrictions which can kill the common cow.
A recent study of the yak genome sheds light on what makes these beasts so well-suited for their hard lives on the high plateaus. The work, published in a recent issue of Nature Genetics, may also help shed light on how humans adjust to high altitude.
The newly <a href="https://www.ncbi.nlm.nih.gov/pubmed/22751099" target="_blank" rel="noopener noreferrer">published</a> yak genome is the work of an international team of researchers headed Qiang Qiu and Jianquan Liu at the Lanzhou University in China.  This first draft of the yak genome proved, unsurprisingly, similar to the already-known cattle genome.  Indeed, the average protein similarity between yak and cattle is 99.5%. Genetic analysis of these two genomes suggest that yaks and cattle diverged approximately 4.9 million years ago, which is comparable to the time at which humans and chimps diverged.
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<img loading="lazy" decoding="async" class="alignleft size-full wp-image-12163" style="float: left; margin-right: 15px;" src="https://blog-api.23andme.com/wp-content/uploads/2012/04/JRBgdIBXKIeVIdETJrxYIw_ttam_logo.jpg" alt="" width="24" height="40" /> What about high-altitude adaptation in humans? Check out this previous Blog<a href="https://blog.23andme.com/news/breathless-over-new-finding-using-ancient-dna/"> post</a>!
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It is, however, the differences rather than the similarities between yaks and cattle which are most illuminating.  The researchers found that three genes related to hypoxia response were selected for in yaks but not in cattle.  Hypoxia is a condition triggered by low oxygen and is a serious concern for cattle living in high-altitude, low-oxygen environments.  One of the yak hypoxia genes (ADAM17) is particularly interesting because certain mutations in the human version of this gene are more common in high-elevation Tibetans than those living at lower elevations.
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In addition to genes involved in hypoxia response, yaks seem especially evolved to deal with nutritional hardships. The researchers found five genes selected for in yaks that help them deal with limited food resources.  These genes help yaks metabolize sugars, fats and proteins as well as regulate the amount of stomach acid produced and perhaps help the yak utilize nitrogen better.
The yak is an adaptive creature, and its genetic differences from cattle help clarify how they manage to live on the harsh, high plateaus. Although more research is needed, the yak and his DNA may eventually provide a window into better understanding high altitude sickness in humans. Now, I’d drink some [yak-butter tea] to that!

Yakking about Yaks

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Watching the Olympics, I am awed by the athleticism of the contestants: they compete with strength, skill and coordination that I could hardly dream of possessing. Certainly hard work and determination has played a role in each athlete’s story, but probably good genes have also contributed to their success.
And if <a href="https://www.23andme.com/topics/wellness/muscle-composition">genetics plays a role in human athletics</a>, it plays an even greater role in the success of animal athletes who are bred with performance in mind. Alaskan sled dogs were once just working dogs, but over the years have been carefully bred into a class of elite four-legged athletes.
Heather Huson and Elaine Ostrander from the National Institutes of Health (NIH) have lead a team of researchers from the NIH, the University of Alaska Fairbanks, and the University of California, Irvine to discover what makes a great dog athlete. Using the tools of modern genetics, they have addressed several questions. Are there genetic differences between sprinters and distance racers? Are there genetic differences between the “top dogs” and those that finish second? Their study&#8217;s findings were recently published in Mammaliam Genome. 

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<img loading="lazy" decoding="async" class="alignleft size-full wp-image-12163" style="float: left; margin-right: 15px;" src="https://blog-api.23andme.com/wp-content/uploads/2012/04/JRBgdIBXKIeVIdETJrxYIw_ttam_logo.jpg" alt="" width="24" height="40" /> To date, more than 150 genes have been linked to different aspects of physical performance in humans. One of the clearest associations is seen with a gene called ACTN3 that is normally turned on in a type of muscle fiber used for power-based sports. A single SNP can turn this gene off. 23andMe customers can see their muscle performance report to see if they are more genetically predisposed to be a sprinter or a endurance athlete.
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Alaskan sled dogs do not belong to one pure breed, but rather are a blend of several different purebred breeds that were combined to optimize for strength, speed, and trainability. Using genetic ancestry analysis, the team of researchers were able to confirm that sprinter and long distance racer dogs have significant differences in their breed blends. Using purebred Alaskan malamute, Siberian huskies, German shorthaired pointers, and borzois for reference, they established that sprinter dogs have a considerably larger dose of German shorthaired pointer ancestry and long-distance race dogs have more Alaskan malamute and Siberian husky ancestry. The authors suggest that dogs with more husky ancestry have more “mental toughness,” a necessity for the long hauls, whereas dogs with more pointer ancestry may be easier to train and are more eager to please and perform.
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Heather Huson: 
Scientist and Sled-Dog Racer 
Heather Huson, one of the leading researchers in this study, is a not only a scientist but also sled dog racing enthusiast.   Having qualified for the US Olympic team twice, she comes at this research with first hand knowledge. You can read more about Huson&#8217;s accomplishments &#8212; both at the bench and on the snow <a href="https://www.google.com/url?sa=t&amp;rct=j&amp;q=&amp;esrc=s&amp;source=web&amp;cd=1&amp;ved=0CGMQFjAA&amp;url=http%3A%2F%2Fwww.nih.gov%2Fcatalyst%2F2010%2F10.12.01%2Fcatalyst_v18i6.pdf&amp;ei=CvMfUM2HMa3SiAKKyoDIAg&amp;usg=AFQjCNHZ2VyBKqB3LnwDp-l2FVmil6rb3w">here (downloadable pdf)</a>.
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The researchers also did a genome-wide association study looking for genetic factors that influence heat tolerance in both sprinters and in long-distance racers.  They found that seven SNPs within one gene &#8212; MYH9 &#8212; were associated with the ability to perform well even in the heat. The dog days of summer perhaps don’t feel so hot for these lucky pooches. There is a similar version of this gene in humans, but more research is needed to determine whether variation in this gene affects human heat tolerance.
As we watch the Olympics in London this summer, we won’t see any four-legged friends on the winner’s podium. Nevertheless, Alaskan sled dogs are tremendous athletes, and genetic studies such as this one may offer insights into the amazing athletic talents of those who actually will be on the podium.
<img loading="lazy" decoding="async" class="aligncenter wp-image-14805 size-full" src="http://35.88.189.111/wp-content/uploads/2012/08/RaceDogImage.jpg" alt="" width="1981" height="1229" srcset="https://blogcms.23andme.com/wp-content/uploads/2012/08/RaceDogImage.jpg 1981w, https://blogcms.23andme.com/wp-content/uploads/2012/08/RaceDogImage-300x186.jpg 300w, https://blogcms.23andme.com/wp-content/uploads/2012/08/RaceDogImage-768x476.jpg 768w, https://blogcms.23andme.com/wp-content/uploads/2012/08/RaceDogImage-1024x635.jpg 1024w, https://blogcms.23andme.com/wp-content/uploads/2012/08/RaceDogImage-880x546.jpg 880w, https://blogcms.23andme.com/wp-content/uploads/2012/08/RaceDogImage-1180x732.jpg 1180w" sizes="auto, (max-width: 1981px) 100vw, 1981px" />
Alaskan sled dogs are a mixture of many purebred breeds. Generally speaking, the relative amounts of these different breeds varies according the type of racing &#8212; sprinter dogs tend to have more German shorthaired pointer ancestry and long-distance race dogs often have more Alaskan malamute and Siberian husky ancestry.

Canine Olympians

As far as disease names go, cancer appears to be pretty simple. Breast cancer is a cancer of the breast, and prostate cancer is a cancer of the prostate.
Although this naming system describes where cancer starts out, it doesn’t tell us much about where cancer will spread, which drugs (if any) will work, if the patient will have a bad reaction to therapy, or whether the patient is likely to survive cancer.
<h2>Going Deeper</h2>
To understand these questions, we need to drill deeper and analyze the molecular barcode of both the cancer and the host.
Understanding the molecular profile of a cancer cell can help physicians understand which drugs will be effective in treating the cancer.
The underlying code for what the cancer “shows” to the rest of the body and how it will behave in the body depends on the DNA inside the cancer cells. And what’s becoming evident is that cancer is much more complicated than we used to think.
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Changes in DNA Underlie Cancer 
Cancer develops when normal cells in the body grow and reproduce uncontrollably because of “mistakes” in the DNA code. DNA (a copy of which is contained in each cell) contains finely tuned instructions for cell growth and production, but as cells copy and pass on this DNA they sometimes make mistakes. These mistakes are technically called “mutations” and cause the DNA to be slightly different from the original.
<img loading="lazy" decoding="async" class="alignright wp-image-14832 size-medium" title="Somatic mutation" src="http://35.88.189.111/wp-content/uploads/2012/08/Somatic-mutation-300x149.png" alt="" width="300" height="149" srcset="https://blogcms.23andme.com/wp-content/uploads/2012/08/Somatic-mutation-300x149.png 300w, https://blogcms.23andme.com/wp-content/uploads/2012/08/Somatic-mutation-768x381.png 768w, https://blogcms.23andme.com/wp-content/uploads/2012/08/Somatic-mutation.png 807w" sizes="auto, (max-width: 300px) 100vw, 300px" />
The mutations that make cells grow too much and thereby cause cancer arise in the course of a person’s lifetime (as opposed to being a change in the DNA that the person is born with) and are called “somatic” mutations.
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<h2>Subtypes</h2>
Under each cancer umbrella, there are actually many different rare diseases. Take breast cancer as an example. By most accounts there are four<a href="http://ww5.komen.org/BreastCancer/SubtypesofBreastCancer.html"> established subtypes</a>, defined based on how the cancer “looks”, both as you would view it under a microscope and on the molecular level.
For instance, a “HER2+” cancer displays the “Human Epidermal Growth Factor Receptor 2” (HER2) molecule on its surface but doesn’t display the estrogen receptor (ER) or progesterone receptor (PR), molecules that catch certain hormones as they pass by.
Cancers overexpressing HER2 can be treated with specific drugs targeting the HER2 molecule. But if breast cancer is triple negative, meaning it doesn’t display any of these three receptors (HER, ER, or PR), then drugs that target these molecules won’t be effective against the cancer.
<h2>Genetics Informed Clinical Trials</h2>
The DNA that someone is born with differs in various places from person to person (so-called “germline” variation) and can also impact the course of treatment.
Most clinical trials performed today do not incorporate genetic testing into the trial&#8217;s design. When they discover that some trial participants react poorly while others are super responders, they look to data points such as age, other diseases the patient is suffering from, or medications he or she is taking. But the explanation may lie deep down in the DNA &#8212; subtle differences in the barcode might be enough for some trial participants to develop an adverse reaction while other people taking the drug derive benefit without harm.
Scientists are now learning more about different cancers by characterizing the mutations driving the tumor and a person&#8217;s unique variants that he or she was born with. The course of cancer depends on both the signature of the tumor, something that stems from you but takes on its own life, and you – the host – a necessary participant in the fight against cancer.

The Molecular Barcode of Cancer – Targeting Treatment to Patient

Editor&#8217;s Note: This post does not reflect the <a href="https://www.23andme.com/topics/health-predispositions/hereditary-hemochromatosis/">current product offering</a> for customers in the United States. 
Mutations in the HFE gene cause most forms of <a href="https://www.23andme.com/topics/health-predispositions/hereditary-hemochromatosis/">hereditary hemochromatosis</a> – a common genetic condition that increases a person’s risk for iron overload and can lead to liver disease, arthritis and heart problems. HFE-related hemochromatosis is recessive, meaning that you must inherit a mutated gene from each parent to have the condition.<img loading="lazy" decoding="async" class="alignright size-medium wp-image-27487" src="https://blog-api.23andme.com/wp-content/uploads/2012/07/HFE-300x177.jpg" alt="" width="300" height="177" srcset="https://blogcms.23andme.com/wp-content/uploads/2012/07/HFE-300x177.jpg 300w, https://blogcms.23andme.com/wp-content/uploads/2012/07/HFE-768x452.jpg 768w, https://blogcms.23andme.com/wp-content/uploads/2012/07/HFE-1024x603.jpg 1024w, https://blogcms.23andme.com/wp-content/uploads/2012/07/HFE-880x518.jpg 880w, https://blogcms.23andme.com/wp-content/uploads/2012/07/HFE-1180x695.jpg 1180w, https://blogcms.23andme.com/wp-content/uploads/2012/07/HFE.jpg 1708w" sizes="auto, (max-width: 300px) 100vw, 300px" />
23andMe customers have long been able to find out their results for two hemochromatosis-causing mutations in the HFE gene: the C282Y mutation and the milder H63D mutation. We’ve now updated our report to include results for a third mutation (S65C) in the genetic results table. The report was also updated to reflect current scientific consensus and to be clearer for our customers.
All three of these mutations are relatively common – 10-30% of people with European ancestry have at least one of them. But only people with two copies of C282Y (or one C282Y mutation plus one H63D or S65C mutation) are prone to accumulating too much iron. 

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Why is Hemochromatosis so Common? 
Roughly one in 300 people with European ancestry has hereditary hemochromatosis. Rates are even higher in certain groups such as Irish, Australian, and Swedish.
The fact that hereditary hemochromatosis is so common has prompted scientists to speculate that despite the dangers of high iron levels, there was at some point in the evolutionary past an advantage to having the genetic change that underlies this condition.
Several (currently unproven) theories have been proposed.
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<li>Variation in the HFE gene arose as people began farming and increased their consumption of cereal grains, which are lower in iron than red meat that predominated in stone age diets.</li>
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<li>Increased iron levels were advantageous because they protect women against iron deficiency brought on by menstruation and childbirth.</li>
<li>Another theory takes into account the fact that hemochromatosis actually leads to a reduction of iron levels in a certain immune cell (the macrophage), which in turn may have given people an advantage by making them resistant to certain infections.</li>
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It can sometimes be confusing to interpret your results for this condition because most people prone to iron overload never show outward signs of the condition. Symptoms also vary widely – from fatigue, to hormone problems, to heart and liver disease – and are influenced by a person’s mutation type, sex, and diet. Age also plays a big role since iron can accumulate in the body over time – if symptoms develop at all, they typically appear later in life between the ages of 40 and 60 in men and after menopause in women.
So what does it mean if you have two mutations linked to hemochromatosis and what should you do with this information?
The short answer is that further testing is recommended. Physicians can order blood tests to measure transferrin saturation and serum ferritin levels in blood, which together provide a good picture of iron absorption and storage in the body. If these markers are elevated, additional testing to determine the impact on organs may also be warranted.
The good news is that the serious symptoms linked to this condition are very rare and highly preventable. Finding out that you have two mutations in the HFE gene early in life can help you make lifestyle changes under the guidance of your physician – forgoing iron supplements and cutting back on iron-rich food – and/or undergo simple treatments to prevent symptoms from developing in the future.
Find out more about Hereditary Hemochromatosis <a href="https://www.23andme.com/topics/health-predispositions/hereditary-hemochromatosis/">here</a>.
July is National Hemochromatosis Month. Check out other posts on this condition: 
&#8211;<a href="../inside-23andme/learning-about-my-risk-for-iron-overload/">Learning About My Risk for Iron Overload</a> 
&#8211;<a href="https://blog.23andme.com/articles/the-iron-scale-factors-tipping-towards-overload"> The Iron Scale: Factors Tipping Towards Overload</a> 
&#8211; <a href="../inside-23andme/health-2/blood-simple/">Battling Against A Common Genetic Disease</a> 
&#8211;<a href="../inside-23andme/health-2/the-most-common-genetic-disease/"> The Most Common Genetic Disease</a>

Health + Traits — Page 28