<img loading="lazy" decoding="async" class="aligncenter size-medium wp-image-3613" title="Grandparent and daughter" alt="" src="https://blog-api.23andme.com/wp-content/uploads/2009/05/istock_000004109962xsmall-300x245.jpg" width="300" height="245" srcset="https://blogcms.23andme.com/wp-content/uploads/2009/05/istock_000004109962xsmall-300x245.jpg 300w, https://blogcms.23andme.com/wp-content/uploads/2009/05/istock_000004109962xsmall.jpg 383w" sizes="auto, (max-width: 300px) 100vw, 300px" />
<a href="http://www.23andme.com/topics/health-predispositions/hereditary-hemochromatosis/">Hereditary hemochromatosis</a> is a common genetic condition that makes a person more prone to absorbing too much iron. Premenopausal women are largely protected from iron overload because of menstruation and pregnancy, but typically around menopause some women begin to experience symptoms of the condition.
A <a href="http://annals.org/article.aspx?articleid=710670">study</a> published in the late 1990’s with 176 women and 176 men with hemochromatosis, matched by age, found that a significant number of the women suffered serious complications from hemochromatosis, and developed their first symptoms only a little later than the men. On average, the women in the study showed symptoms around age 50, while the men showed signs nearly two years earlier. Roughly half of the women had stopped menstruating at the time of diagnosis, but the other half were technically premenopausal at diagnosis. There was some evidence that women who stopped menstruating before the age of 50 had higher levels of iron in their bodies.
For certain conditions*, like cirrhosis and diabetes, rates were higher in men, but for others, like fatigue and arthritis, rates were higher in women. Roughly 94 percent of the women, versus 100 percent of men, had abnormal measures of iron stores in the body.
<div style="float: right; text-align: justified; width: 200px; padding: 15px; border: 1px solid #ccc; margin-left: 10px;">Women and Men Have the Same Genetic Risk for Hemochromatosis 
Hereditary hemochromatosis affects women and men equally with respect to how the condition is inherited: you must inherit a mutated gene from each parent to have the condition and the gene involved in most forms of hereditary hemochromatosis, the HFE gene, is not located on the sex chromosomes. (This condition is autosomal recessive.) 
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Thus, the results from this study suggest that women can suffer overt symptoms of hereditary hemochromatosis and at roughly the same age as men. And once a woman goes through menopause and loses her natural way of expelling iron, she appears to have more or less the same risk as a man for suffering serious complications including arthritis and liver disease.
For most women menopause is associated with <a href="http://my.clevelandclinic.org/disorders/menopause/hic_menopause_the_short-term_effects_and_long-term_risks.aspx">various changes in health</a>. In the short term women can attest to unpleasantries that result from drops in estrogen levels. High on the list are hot flashes, changes in sex drive, and mood changes. But there are also serious long term risks for conditions like osteoporosis and heart disease. For women with hereditary hemochromatosis, increased risk for absorbing too much iron should also be added to the list. Women should take note that the symptoms of menopause and hemochromatosis can sometimes overlap, for instance fatigue is common to both.
Whether before or after menopause, it’s important for women with hereditary hemochromatosis to monitor the iron levels in their body. 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.
*Liver cirrhosis occurred in ~14 percent of the women and 26 percent of the men; diabetes occurred in ~7 percent of the women and ~16 percent of the men; fatigue occurred in ~65 percent of the women and 42 percent of the men; arthritis occurred in ~45 percent of the women and ~35 percent of the men.

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23andMe Blog

23andMe Blog Team

Hemochromatosis in Women Before and After Menopause

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For a long time prospective fathers could wile away the years without much worry about when to have kids, while prospective moms were constantly checking their ticking biological clocks.
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<div>A<a href="https://www.nature.com/nature/journal/v488/n7412/full/nature11396.html"> recent study</a> may turn the tables a bit. It may push men to think a little more about how long they wait to start a family.The study by DeCODE in Iceland shows that each year a man delays fatherhood he increases the number of new genetic mutations that he passes on to his children.
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<h2>A Calculation</h2>
<div>These “de novo” mutations are not ones that the father was born with. Therefore they are unrelated to any previous family history or condition. They occur spontaneously in the father’s sperm cells.Using the data from the study, 23andMe’s Emily Chang lead the team that  created a simple tool that uses a man’s age to calculate the number of mutations he might pass on to his children.
<img loading="lazy" decoding="async" class="aligncenter wp-image-15995 size-full" title="mutation small" src="http://35.88.189.111/wp-content/uploads/2012/09/mutation-small.jpg" alt="" width="253" height="406" srcset="https://blogcms.23andme.com/wp-content/uploads/2012/09/mutation-small.jpg 253w, https://blogcms.23andme.com/wp-content/uploads/2012/09/mutation-small-187x300.jpg 187w" sizes="auto, (max-width: 253px) 100vw, 253px" />
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<div>So what does the number mean?</div>
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<div>The<a href="https://www.nytimes.com/2012/08/23/health/fathers-age-is-linked-to-risk-of-autism-and-schizophrenia.html"> implication from the study</a> is that the longer a man waits the more he increases the chances his child might develop certain kinds of conditions, such as autism. While the risk may increase, it is still very low.Also, keep in mind that despite the name, mutations are not necessarily bad. In fact, these different spellings within a person’s genetic code are largely benign. Some may even be beneficial and lead to long term genetic diversity among people.
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<h2>A Risk for Autism?</h2>
Science writer Alok Jha pointed out in a<a href="http://www.guardian.co.uk/science/2012/aug/22/older-fathers-genetic-mutations-research"> piece in the Guardian</a> that a single mutation in the APP gene actually protects against Alzheimer’s disease. It also helps people live longer. At the same time, some preliminary studies suggest that the more de novo mutations passed onto a child the higher the risk that child could develop certain types of conditions, such as autism and schizophrenia.
<div>Or as lead author Kari Stefansson, deCODE’s chief executive,<a href="https://www.nature.com/news/fathers-bequeath-more-mutations-as-they-age-1.11247"> told Ewen Callaway at Nature</a>:</div>
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“The older we are as fathers, the more likely we will pass on our mutations. The more mutations we pass on, the more likely that one of them is going to be deleterious.”
For women, who pass on other risks to their children with age, the number of de novo mutations a mom passes on to a child is constant at about 14. The number of new mutations a father passes to a child goes up by two each year. That means that a 50-year-old new father might pass on about 65 new mutations to his child. A father half his age would pass on about 35 mutations. The reason the number of de novo mutations women and men pass on to their children is so different is because women are born with all their eggs. Men on the other hand produce sperm throughout their lifetime, offering more opportunities for mutations to occur.
This doesn’t necessarily mean that men should start having kids or having their sperm frozen right out of college. But it does add more information for prospective fathers to consider. It also gives us a little more understanding about complex conditions like autism.
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Older Dads

<img loading="lazy" decoding="async" class="alignright size-thumbnail wp-image-5677" title="alzheimers" alt="" src="https://blog-api.23andme.com/wp-content/uploads/2009/12/alzheimers-150x150.jpg" width="150" height="150" srcset="https://blogcms.23andme.com/wp-content/uploads/2009/12/alzheimers-150x150.jpg 150w, https://blogcms.23andme.com/wp-content/uploads/2009/12/alzheimers-271x271.jpg 271w" sizes="auto, (max-width: 150px) 100vw, 150px" />
In honor of World Alzheimer’s Day, we’re linking to a few posts and stories about the disease. Alzheimer’s disease is the most common form of dementia and affects more than 35 million people worldwide.
23andMe first began allowing customers to learn about their genetic risk for late-onset Alzheimer’s disease a little more than a year ago. We report on variants of the<a href="https://www.23andme.com/health/alzheimers/"> APOE</a> gene (e2, e3, and e4) and provide a risk estimate for the disease for customers with European ancestry. The 23andMe report also includes detailed background information on Alzheimer’s including other known risk factors for the disease, such as obesity and high cholesterol.
Although some are critical of giving people access to this information, many people say that despite their fear of Alzheimer’s they<a href="https://www.washingtonpost.com/national/health-science/despite-fears-of-alzheimers-many-would-like-to-know-their-risk-for-the-disease/2012/08/10/438eb3ba-6a2c-11e1-acc6-32fefc7ccd67_story.html"> would rather know</a> their risk than remain in the dark about the danger. For some knowing their APOE status and Alzheimer’s risk may encourage them to engage in <a href="http://well.blogs.nytimes.com/2012/01/18/how-exercise-may-keep-alzheimers-at-bay/">activities to stave off</a> the disease, or prompt them to participate in clinical research that could lead to more information about the causes and possible cures for Alzheimer’s.
Recently, scientists discovered a rare genetic variant that may be protective against the disease. In people of Icelandic descent, the T version of the variant (also known as the A673T variant in the APP gene) was associated with about five times lower odds of Alzheimer’s. This finding was <a href="https://www.nature.com/nature/journal/v488/n7409/abs/nature11283.html">first reported in the journal Nature</a> over the summer.
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World Alzheimer’s Day

by Emily Chang, Joanna Mountain, and Mike Macpherson
<img loading="lazy" decoding="async" class="alignright wp-image-15198 size-medium" src="http://35.88.189.111/wp-content/uploads/2012/08/Haplogroup10-300x193.jpg" alt="" width="300" height="193" srcset="https://blogcms.23andme.com/wp-content/uploads/2012/08/Haplogroup10-300x193.jpg 300w, https://blogcms.23andme.com/wp-content/uploads/2012/08/Haplogroup10-768x495.jpg 768w, https://blogcms.23andme.com/wp-content/uploads/2012/08/Haplogroup10-1024x660.jpg 1024w, https://blogcms.23andme.com/wp-content/uploads/2012/08/Haplogroup10-880x567.jpg 880w, https://blogcms.23andme.com/wp-content/uploads/2012/08/Haplogroup10-1180x760.jpg 1180w" sizes="auto, (max-width: 300px) 100vw, 300px" /> 
 Click on the image above for a larger version of this chart, which shows that some ancestry combinations are more common than others in the 23andMe database.
Given the United States&#8217;s “melting pot” nature, it is not surprising that most Americans have mixed ancestry.
Like many of my fellow citizens, my ancestry is a long recipe: a bit of English, a dash of German, a pinch of Hungarian. Should my husband and I have kids, my children will have Chinese ancestry, too. Such mixed ancestry is becoming increasingly the norm, and genetics turns out to be a very useful tool to explore it.
Traditionally, genetic ancestry focused on two particular pieces of DNA, mitochondrial DNA and the Y-chromosome.  Your maternal line includes your mother, your maternal grandmother, her mother before her, and so on; likewise, your paternal line includes your father, your paternal father, his father before him, and so on. The paternal line is determined using the Y chromosome, which determines whether a person is male and only men can pass down. The maternal line is determined using the DNA found inside mitochondria, small energy-producing cellular machines with their own genetic blueprints.
Both men and women have mitochondrial DNA, but only women pass on their mitochondrial DNA to children.
These days, genetic ancestry tools like 23andMe use DNA from all of your 23 pairs of chromosomes to offer insights into your heritage.  However, information about maternal and paternal lines, which can reflect ancestral origins, can yield interesting insights.
<img loading="lazy" decoding="async" class="alignright wp-image-15199 size-medium" src="http://35.88.189.111/wp-content/uploads/2012/08/MaternalPaternalLines-300x283.jpg" alt="" width="300" height="283" srcset="https://blogcms.23andme.com/wp-content/uploads/2012/08/MaternalPaternalLines-300x283.jpg 300w, https://blogcms.23andme.com/wp-content/uploads/2012/08/MaternalPaternalLines.jpg 400w" sizes="auto, (max-width: 300px) 100vw, 300px" /> This figure shows the paternal line in blue and the maternal line in pink. Your maternal grandmother and paternal grandfather are members of your maternal and paternal lines, respectively.
Our large customer database shows that some ancestry combinations are more common than others among our customers. Given a pair of ancestral origins, there are two ways to combine the maternal and paternal lines: a maternal line of the first ancestry with a paternal line of the second ancestry or a paternal line of the first ancestry with a maternal line of the second ancestry.
Our database shows that these two ways of combining the maternal and paternal lines are not equally common, indicating gender trends in mating. For instance, about 3.5 times as many 23andMe customers have a maternal line indicative of African ancestry and a paternal line indicative of European ancestry than the reverse. This mating trend probably reflects, in part, a disgraceful period in the United States&#8217; past in which white male slave owners fathered children with enslaved African American women rather than recent trends in interracial marriages. More recent marriage patterns actually reflect a trend in the opposite direction.
The 2010 US census shows that a “white” wife and “black” husband is 2.3 times more common than a “white” husband and “black” wife [note: the terms “black” and “white” were the descriptors used in the US census report].
The maternal and paternal lines of the 23andMe customers, thus, tell the sad truth of the treatment of enslaved African American women. In one episode of the television program Finding Your Roots, Condoleezza Rice says this aspect of United States history is an “unhealed wound in America” and that we have trouble talking about what really happened during slavery. She is right. Most of us would rather not talk about the rape of enslaved African American women, but DNA isn’t shy about addressing this ugly truth. As we study and learn about these genetic patterns, we face one of the most disturbing aspects of United States history &#8212; a vital step towards healing that unhealed wound to which Rice referred.
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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" /> Learn more about <a href="https://www.23andme.com/you/ancestry">your ancestry</a> in your  23andMe account.
Not yet a customer? Visit our <a href="https://www.23andme.com/store/cart/">store</a> or <a href="https://www.23andme.com/ancestry">learn more</a>.
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A similar but less extreme pattern was observed for individuals of Asian and European ancestry; about 1.7 times as many 23andMe customers have a European paternal line in conjunction with an Asian maternal line than have an Asian paternal line with a European maternal line. The reason for this particular mating trend can not be traced to slavery and may have more complex sociological and historical origins.  Regardless of its source, however, the trend is supported by other studies. The large <a href="http://www.pewsocialtrends.org/2012/02/16/the-rise-of-intermarriage/">PEW study</a> on interracial marriage released this past February which observed that Asian American women were more likely to have an interracial marriage than Asian American men, and the US Census Bureau, which captures a wider segment of our society than the 23andMe database, shows an even stronger trend &#8212; a “white” husband and “Asian” wife is 2.4 times more common than a “white” wife and “Asian” husband [note: the terms “Asian” and “white” were the descriptors used in the US census report].
Our DNA holds a lot of information. It tells us who we are and who we, collectively, were. The mating trends seen in the maternal and paternal lines of 23andMe customers reflect complex sociological and historical truths, even some historical truths that are difficult to face. Genetics helps us learn more about who we are and who we were, hoping that such knowledge will translate into less racism and more appreciation for people who are different from ourselves.

Emily Chang

Who Planted The Family Tree?

We know you’ve been studying hard at 23andMe U., but you’ve still got one more quiz to complete. 
This one hinges on some of the genetic differences between men and women.
So before you matriculate, here’s the last quiz. Now don’t sweat it, you’ll do fine and we’ll even give you some hints along the way to help!
You’ve learned that we all have 23 pairs of chromosomes. If you were paying attention in the last quiz you’ll know that 22 of those pairs contain the <a href="https://www.23andme.com/gen101/origins/">same genes on each chromosome</a> and are called “autosomes”. These question are about the all-important 23rd pair of chromosomes. Watch the videos and then test your knowledge.
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<td style="padding: 15px;"><img loading="lazy" decoding="async" class="alignright size-medium wp-image-15324" title="where genes come from" src="https://blog-api.23andme.com/wp-content/uploads/2012/08/where-genes-come-from-300x222.jpg" alt="" width="300" height="222" /></td>
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<h3><a href="https://www.khanacademy.org/science/biology/v/genetics-101-part-3--where-do-your-genes-come-from" target="_blank" rel="noopener noreferrer">Genetics 101 Part 3: Where Do Genes Come From</a></h3>
Description: 
Find out how chromosomes and genes are passed down from parent to child.
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4 min 20 sec
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<td style="padding: 15px;"><img loading="lazy" decoding="async" class="alignright size-medium wp-image-15325" title="why no why" src="https://blog-api.23andme.com/wp-content/uploads/2012/08/why-no-why-300x220.jpg" alt="" width="300" height="220" srcset="https://blogcms.23andme.com/wp-content/uploads/2012/08/why-no-why-300x220.jpg 300w, https://blogcms.23andme.com/wp-content/uploads/2012/08/why-no-why.jpg 483w" sizes="auto, (max-width: 300px) 100vw, 300px" /></td>
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<h3><a href="https://www.youtube.com/watch?v=QCm2x9OABI8" target="_blank" rel="noopener noreferrer">Genetics 101 Part 5: Why No Why?</a></h3>
Description: 
Find out why women don&#8217;t have a Y chromosome, but can still learn about their paternal ancestry.
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1 min 10 sec
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Update: This quiz is officially over! <a href="https://blog.23andme.com/23andme-and-you/back-to-school-sex-chromosomes-quiz-results/" target="_blank" rel="noopener noreferrer">Check out the answers here.</a>
<div style="border: 1px solid #000; padding: 5px; font-style: italic; margin: 15px; width: 550px; float: center;">
<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" />You have now completed the 23rd Chromosome quiz. Click on the certificate below and get a larger image which you can print out and display it with pride.
<img loading="lazy" decoding="async" class="aligncenter size-medium wp-image-15341" title="CertificateXY" src="https://blog-api.23andme.com/wp-content/uploads/2012/08/CertificateXY-300x198.jpg" alt="" width="300" height="198" srcset="https://blogcms.23andme.com/wp-content/uploads/2012/08/CertificateXY-300x198.jpg 300w, https://blogcms.23andme.com/wp-content/uploads/2012/08/CertificateXY-768x508.jpg 768w, https://blogcms.23andme.com/wp-content/uploads/2012/08/CertificateXY.jpg 841w" sizes="auto, (max-width: 300px) 100vw, 300px" />
Want to continue your education? You can learn about <a href="https://www.23andme.com/you/" target="_blank" rel="noopener noreferrer">yourself from both a health and ancestry perspective </a> on 23andMe. Not yet a customer? Visit our <a href="https://www.23andme.com/store/cart/" target="_blank" rel="noopener noreferrer">store</a>.
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Back to School: All About Sex… Chromosomes

<img loading="lazy" decoding="async" class="alignright size-medium wp-image-6445" title="elderly_1" src="https://blog-api.23andme.com/wp-content/uploads/2010/04/elderly_1-300x199.jpg" alt="" width="300" height="199" srcset="https://blogcms.23andme.com/wp-content/uploads/2010/04/elderly_1-300x199.jpg 300w, https://blogcms.23andme.com/wp-content/uploads/2010/04/elderly_1.jpg 425w" sizes="auto, (max-width: 300px) 100vw, 300px" />
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.
Not yet a customer? <a href="https://www.23andme.com/store">Visit our store</a>!
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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.

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.
<img loading="lazy" decoding="async" class="aligncenter wp-image-15553" title="Avoidance of Errors" src="https://blog-api.23andme.com/wp-content/uploads/2012/09/Avoidance-of-Errors.png" alt="" width="393" height="740" srcset="https://blogcms.23andme.com/wp-content/uploads/2012/09/Avoidance-of-Errors.png 393w, https://blogcms.23andme.com/wp-content/uploads/2012/09/Avoidance-of-Errors-159x300.png 159w" sizes="auto, (max-width: 393px) 100vw, 393px" /><a href="https://blog-api.23andme.com/wp-content/uploads/2012/09/Avoidance-of-Errors1.png"> 
</a><a href="https://blog-api.23andme.com/wp-content/uploads/2012/09/Avoidance-of-Errors.png"> 
</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 

<img loading="lazy" decoding="async" class="aligncenter wp-image-15614" title="Dopamine receptor polymorphism" src="https://blog-api.23andme.com/wp-content/uploads/2012/09/Dopamine-receptor-polymorphism-300x290.jpg" alt="" width="300" height="290" srcset="https://blogcms.23andme.com/wp-content/uploads/2012/09/Dopamine-receptor-polymorphism-300x290.jpg 300w, https://blogcms.23andme.com/wp-content/uploads/2012/09/Dopamine-receptor-polymorphism.jpg 638w" sizes="auto, (max-width: 300px) 100vw, 300px" />
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

<img loading="lazy" decoding="async" class="alignright wp-image-15595 size-medium" title="DNA-bases" src="http://35.88.189.111/wp-content/uploads/2012/09/DNA-bases-300x226.png" alt="" width="300" height="226" srcset="https://blogcms.23andme.com/wp-content/uploads/2012/09/DNA-bases-300x226.png 300w, https://blogcms.23andme.com/wp-content/uploads/2012/09/DNA-bases.png 607w" sizes="auto, (max-width: 300px) 100vw, 300px" />
Attention all students! We&#8217;re extending the Genetics 101 quiz through Sunday, September 16th to give everyone plenty of time to brush up on their genetics and earn a chance to win a $25 Amazon gift card!
If you already filled out the quiz and weren’t prompted to enter your name and email address (or you aren&#8217;t sure if you did), please take the time to fill it out again. We apologize for the inconvenience!
<a href="https://blog.23andme.com/articles/learn-genetics-101">Take the Genetics 101 quiz. </a>

Genetics Quiz Extended

<div style="float: right; text-align: justified; width: 200px; background-color: #eee; padding: 15px; margin-left: 10px;"><img loading="lazy" decoding="async" class="aligncenter wp-image-15470 size-thumbnail" title="Gregor" src="http://35.88.189.111/wp-content/uploads/2012/08/Gregor-150x150.jpg" alt="" width="150" height="150" srcset="https://blogcms.23andme.com/wp-content/uploads/2012/08/Gregor-150x150.jpg 150w, https://blogcms.23andme.com/wp-content/uploads/2012/08/Gregor-271x271.jpg 271w" sizes="auto, (max-width: 150px) 100vw, 150px" />Our Hero 
Gregor Mendel, an Austrian monk and biologist, worked out the pattern of inheritance of various traits. He showed that a “dominant” trait is one that always shows up in offspring while a “recessive” trait is one that is masked by a dominant gene.</div>
Update: If you took this quiz before 10 a.m. PST on Monday, September 10th, we neglected to capture your name and email address. We sincerely apologize for this oversight. Please fill out the quiz again and this time you will be prompted to enter your name and email. We&#8217;ve extended this quiz through 11:59 p.m. PST September 16th to give you plenty of time!   
Pop quiz.  Who was Gregor Mendel?
If only hazy visions of pea pods come to mind you might want to buff up on your biology.
Learning about genetics isn’t just for high schoolers and college students – it’s an interesting topic of exploration no matter what your age or profession.
We&#8217;re going to help you with a quick primer and links to some of our online educational videos found on our <a href="https://www.23andme.com/gen101/">website</a>. And to make sure it all sunk in we&#8217;ve got a quiz at the bottom of this post.
What Are Genes? 
DNA contains the instructions for making you and takes the shape of a twisted ladder, having two parallel, but complementary strands. There are four letters to the DNA alphabet – A, T, G and C. Human DNA is organized into two pairs of 23 chromosomes and chromosomes are further organized into short segments of DNA called genes. If you imagine your DNA as a cookbook, then your genes are the recipes. Written in the DNA alphabet, the recipes tell your cells how to function and what traits to express.
Where Do Genes Come From? 
You were gifted with a set of 23 chromosomes from your mom and a set of 23 chromosomes from your dad. Twenty two of the pairs contain the <a href="https://www.23andme.com/gen101/origins/">same genes on each chromosome</a> and are called “autosomes”. The remaining pair is composed of the “sex chromosomes” and isn’t necessarily identical – females typically have two X chromosomes and males have an X and a Y.
What Are Phenotypes? 
Slight variation in your genes is part of what makes you unique. Your observable traits, also known as your phenotypes, result from interactions between your genes and the environment. Differences in some phenotypes, like height, are determined mostly by genes. If you have short parents and grandparents, you probably don&#8217;t tower over your peers, though environmental factors like a healthy diet might give you a little lift. The influence of genes on other traits, such as your personality, is less well understood.
Did you get all that? Take our quiz and find out! Prizes will be given to a random selection of people who answer all questions correctly (perfect for buying that genetics textbook on your wishlist). Good luck!
Update: This quiz is officially over! 
<div style="border: 1px solid #000; padding: 5px; font-style: italic; margin: 15px; width: 550px; float: center;">
<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" />You have now completed the entire 23andMe Genetics 101 course, the second in a three-part Back-to-School educational course series! Click on the certificate below get a larger image which you can print out and display it with pride.
<img loading="lazy" decoding="async" class="aligncenter size-medium wp-image-15549" title="CertificateGenetics" src="https://blog-api.23andme.com/wp-content/uploads/2012/09/CertificateGenetics-300x198.jpg" alt="" width="300" height="198" srcset="https://blogcms.23andme.com/wp-content/uploads/2012/09/CertificateGenetics-300x198.jpg 300w, https://blogcms.23andme.com/wp-content/uploads/2012/09/CertificateGenetics-768x508.jpg 768w, https://blogcms.23andme.com/wp-content/uploads/2012/09/CertificateGenetics.jpg 845w" sizes="auto, (max-width: 300px) 100vw, 300px" /><a href="https://blog-api.23andme.com/wp-content/uploads/2012/08/PreHistoryPostCertificate.jpg" target="_blank" rel="noopener"> 
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Want to continue your education? Learn about <a href="https://www.23andme.com/you/" target="_blank" rel="noopener">your health and ancestry </a>with 23andMe. Not yet a customer? Visit our <a href="https://www.23andme.com/store/cart/" target="_blank" rel="noopener">store</a>.
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