Along with having some very talented scientists and engineers on staff, 23andMe is lucky to have some customers who are equally accomplished.
<div id="attachment_22394" style="width: 297px" class="wp-caption alignright"><img loading="lazy" decoding="async" aria-describedby="caption-attachment-22394" class="size-medium wp-image-22394" src="https://blog-api.23andme.com/wp-content/uploads/2015/04/Ann_cropped_modified-287x300.jpg" alt="Dr. Ann Turner, MD" width="287" height="300" srcset="https://blogcms.23andme.com/wp-content/uploads/2015/04/Ann_cropped_modified-287x300.jpg 287w, https://blogcms.23andme.com/wp-content/uploads/2015/04/Ann_cropped_modified.jpg 355w" sizes="auto, (max-width: 287px) 100vw, 287px" />Dr. Ann Turner, MD</div>
One of those is Dr. Ann Turner, a 23andMe Ancestry Ambassador and physician. Ann was recently listed as a co-author on <a href="http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1005137" target="_blank" rel="noopener">a paper</a> published by researchers from the University of Iowa about a genetic variant involved in hearing loss. It turned out to be in a gene that was not even known to be important for the sense of hearing.
“My main contribution was recruiting enough cousins to isolate the segment that must of necessity harbor the mutation,” said Ann.
What’s inspiring is that the impetus for this research was Ann’s own quest to learn about the genetics behind her and her family’s hearing impairment.
Her own hearing loss started in childhood and got progressively worse over time. She’s been wearing hearing aids for 40 years now. Worldwide hearing impairment impacts over five percent of the population, or about 360 million people. Although many different genetic mutations are involved in hearing loss, in this case the researchers were able to isolate a single mutation involved in this one family’s loss of hearing.
Ann’s own <a href="https://blog.23andme.com/articles/tracking-down-a-trait" target="_blank" rel="noopener">personal search</a> of the genetics behind the trait included work going back more than 20 years. She used traditional genealogical techniques to trace hearing loss back 200 years in her family to an ancestor named John Riley, who was born in 1813. One of her relatives, James Riley, a Civil War veteran, died from a fall after failing to hear a warning from a co-worker that the scaffolding he was on was not secure.
<div id="attachment_22396" style="width: 310px" class="wp-caption alignright"><img loading="lazy" decoding="async" aria-describedby="caption-attachment-22396" class="size-medium wp-image-22396" src="https://blog-api.23andme.com/wp-content/uploads/2015/04/HOMER2_pedigree-300x162.jpg" alt="This is a pedigree Ann did of her family showing how tracing the mutation through generations of her family." width="300" height="162" srcset="https://blogcms.23andme.com/wp-content/uploads/2015/04/HOMER2_pedigree-300x162.jpg 300w, https://blogcms.23andme.com/wp-content/uploads/2015/04/HOMER2_pedigree.jpg 679w" sizes="auto, (max-width: 300px) 100vw, 300px" />This is a pedigree Ann did of her family showing how tracing the mutation through generations of her family.</div>
Beyond paper records and family trees, Ann also used her and her cousins’ 23andMe results to try and track down the genetics behind their hearing condition. She participated in 23andMe’s exome pilot project a few years ago. This allowed her to obtain the sequence data for all the coding regions of all genes, and she was in turn able to use that data to point to candidate mutations possibly involved in her family’s hereditary hearing loss. “Even though this type of testing is not designed to discover rare or novel mutations, I could roughly narrow down the chromosomal region where the mutation must be located,” Ann said. By looking at her and her family member’s data she was able to identify places where only those with hearing loss shared DNA segments.
“It finally boiled down to just one region by the time all of our results were compared. I wrote about this in a blog post for 23andMe,” she said. The candidate mutation is in the HOMER2 gene. Following up on that work, researchers at the University of Iowa did what are called “functional studies” looking at how that specific genetic mutation affected zebrafish and mice in the lab. The researchers initially found that the loss of function of HOMER2 gene caused by this mutation led to changes in hair cells in the lateral line organ of the zebrafish, which detects movement in the surrounding water. In an email Ann sent to the family members who participated in the research she referenced what researchers did next in their study of mice.
“When (the researchers) did a &#8220;knockdown&#8221; of the HOMER2 gene (made it completely non-functional), the mice developed an early onset hearing loss. It was progressive and started in the high frequencies first, just like our family,” she told her family.
“Our data offer novel insights into gene pathways essential for normal auditory function and the maintenance of cochlear hair cells,” according to the paper’s authors. For Ann the finding was both illuminating for her own family’s condition, but also interesting from her point of view as a scientist. “I have a sense of wonder at how this study illustrates the unity of life, with changes in the lateral line organ in fish confirming the functional effect of the mutation,” she said. Ann adds that other families may be able to use 23andMe tests to help identify the cause of some genetic trait or condition.
For Ann the finding was both illuminating for her own family’s condition, but also interesting from her point of view as a scientist.
“I have a sense of wonder at how this study illustrates the unity of life, with changes in the lateral line organ in fish confirming the functional effect of the mutation,” she said. Ann adds that other families may be able to use 23andMe tests to help identify the cause of some genetic trait or condition.
The candidate mutation is in the HOMER2 gene. Following up on that work, researchers at the University of Iowa did what are called “functional studies” looking at how that specific genetic mutation affected zebrafish and mice in the lab. The researchers initially found that the loss of function of HOMER2 gene caused by this mutation led to changes in hair cells in the lateral line organ of the zebrafish, which detects movement in the surrounding water. In an email Ann sent to the family members who participated in the research she referenced what researchers did next in their study of mice.
“When (the researchers) did a &#8220;knockdown&#8221; of the HOMER2 gene (made it completely non-functional), the mice developed an early onset hearing loss. It was progressive and started in the high frequencies first, just like our family,” she told her family.

23andMe Blog

23andMe Blog Team

Citizen Scientist

A new study by researchers from Stanford Medical School and 23andMe is the first to identify genetic variants associated with rosacea, a chronic skin disease estimated to affect more than 16 million people in the United States alone.<img loading="lazy" decoding="async" class="alignright size-medium wp-image-22186" src="https://blog-api.23andme.com/wp-content/uploads/2015/02/Skin-Graphic-300x300.jpg" alt="Skin Graphic" width="300" height="300" srcset="https://blogcms.23andme.com/wp-content/uploads/2015/02/Skin-Graphic-300x300.jpg 300w, https://blogcms.23andme.com/wp-content/uploads/2015/02/Skin-Graphic-150x150.jpg 150w, https://blogcms.23andme.com/wp-content/uploads/2015/02/Skin-Graphic-271x271.jpg 271w, https://blogcms.23andme.com/wp-content/uploads/2015/02/Skin-Graphic-372x372.jpg 372w, https://blogcms.23andme.com/wp-content/uploads/2015/02/Skin-Graphic-574x574.jpg 574w, https://blogcms.23andme.com/wp-content/uploads/2015/02/Skin-Graphic.jpg 600w" sizes="auto, (max-width: 300px) 100vw, 300px" />


Led by <a href="https://stanfordhealthcare.org/doctors/c/annelynn-chang.html" target="_blank" rel="noopener noreferrer">Dr. Anne Lynn S. Chang</a>, of Stanford University’s School of Medicine, the <a href="https://www.nature.com/jid/journal/vaop/naam/abs/jid201553a.html#close" target="_blank" rel="noopener noreferrer">study</a> to be published in the Journal of Investigative Dermatology, is the first to identify genetic factors for this common but incurable condition. (The link is to a pre-print version of the paper.)
Although the genetic basis for rosacea has long been hypothesized, this is the first study to find genetic variants associated with the condition.
The genes identified in the study support the concept of a genetic basis for rosacea and that could in turn help identify new targets for future studies to better understand and treat this condition. 


The discovery portion of the study, which involved the consented participation of more than 22,000 23andMe customers, found two genetic variants strongly associated with the disease among people of European ancestry. Of the 22, 000 customers in this part of the study, more than 2,600 of them had rosacea and the other 20,000 did not have the condition and were used as controls.


Although rosacea is not life threatening, it is a serious and still little understood condition. Some of the symptoms include redness, inflammation, visible blood vessels, pimple like sores on the skin of the central face, as well as burning and itching. Left untreated it can lead to more serious complications, including disfiguring of the nose – called rhinophyma – and damage to the cornea causing vision problems. Because the condition is so visible it can make those who have it feel isolated.
&#8220;This is also another example of how 23andMe can help in researching common yet understudied diseases,” said 
Joyce Tung, PhD, 23andMe’s Director of Research and a co-author of the paper.


Another intriguing finding from this study is that the single nucleotide polymorphisms (SNPs) found to be strongly associated with the condition, are in or near genes associated with other diseases including diabetes and celiac disease.
One of the SNPs found strongly associated with the condition, , is between the genes HLA-DRA and BTNL2. The HLA-DRA gene is involved in histocompatibility and immune response, which is consistent with the inflammatory nature of rosacea.
To validate the association, 23andMe researchers tested the SNPs from the genome-wide association study in a separate group of 29,000 consented 23andMe customers. The researchers were able to confirm the same association with rosacea.
For that portion of the study, researchers looked at more than 3,000 individuals with rosacea and 26,000 controls.
In addition to the genome wide association study that discovered the variants associated with rosacea, Dr. Chang and her team also took skin biopsies from six individuals with rosacea and showed that both HLA-DRA and BTNL2 proteins can be found in the skin of people with rosacea.
This preliminary works hints toward the biological relevance of HLA-DRA and BTNL2 in rosacea.
The genetic associations found in this study and the associations with other diseases like diabetes and celiac disease may help direct future study.

Genetics found to influence risk for rosacea

Grab a tissue for this. Your genes may make you more prone to cry, and if you cry easily you are at higher odds to have been diagnosed with depression, anxiety or bipolar disorder.<img loading="lazy" decoding="async" src="https://blog-api.23andme.com/wp-content/uploads/2015/03/GeneticsOfCryingInfographic_030615-352x768.jpg" alt="GeneticsOfCryingInfographic_030615" class="alignright size-large wp-image-22302" width="352" height="768" />
Looking at data from 200,000 customers who consented to participate in research, 23andMe scientists found a dozen genetic variants associated with whether a person cries easily.
<h6>Emotional Response</h6>
Crying is an emotional response that makes humans unique from other primates. Some would argue it’s what <a href="http://www.scientificamerican.com/article/why-humans-like-to-cry/" target="_blank" rel="noopener noreferrer">makes us human</a>.
But in 23andMe’s study, researchers wanted to look more deeply into the emotional response. They wanted to know whether there were genetic reasons for some of us crying more easily than others.
Some of the research findings were presented last year at the <a href="https://blog.23andme.com/23andme-research/23andmes-research-at-ashg-2014/" target="_blank" rel="noopener noreferrer">American Society of Human Genetics</a> annual conference. But this study includes both genetic and non-genetic associations. For instance, the study found that boys do cry, but just not as much as girls. According to the research women are three times more likely to “cry easily” when compared to men. Both men and women are more prone to cry as they age. That is especially true if one of their parents was more likely to cry easily.
<h6>Brain Development</h6>
Beyond those findings, the study offered some interesting avenues for future study. The variants identified were found in or near genes involved with brain development (IRX2 and ZNF423) , hormone synthesis (HSD17B12) and certain mood disorders (6q16.1). This could help researchers studying affective disorders, among other things.
23andMe offers its customers the opportunity to participate in research if they want. They can also opt out of research at any time. We are thankful to our customers who participated, making this and other studies like it possible.
Learn more about participating in research, or opting out of it, here.

Too Many Teardrops

Whether you are more apt to reach for a handful of potato chips or go for the bowl of candy may have something to do with your genetics.<img loading="lazy" decoding="async" src="https://blog-api.23andme.com/wp-content/uploads/2015/03/Salty-Sweet-2-300x114.jpg" alt="Salty Sweet 2" class="alignright size-medium wp-image-22298" width="300" height="114" srcset="https://blogcms.23andme.com/wp-content/uploads/2015/03/Salty-Sweet-2-300x114.jpg 300w, https://blogcms.23andme.com/wp-content/uploads/2015/03/Salty-Sweet-2.jpg 560w" sizes="auto, (max-width: 300px) 100vw, 300px" />


23andMe scientists identified genetic markers associated with preferring sweet snacks to salty or savoury ones.

 

<h6>Genetics of Taste Preference</h6>
Your age and culture influences the food you like. But genetics plays an important role too.
23andMe customers were evenly split about whether they preferred a <a href="https://www.23andme.com/topics/traits/sweet-salty/">salty snack or a sweet one</a>. But looking at the data, researchers here found several genetic markers associated with preferring sweet snacks over salty ones. 
23andMe’s study found that individuals several variants associated with a preference for sweets.

One of the many interesting aspects of this finding is that both of these genetic markers are in genes that are associated either with metabolism or body mass.
The marker is in the gene FGF21 and the other marker is located in the FTO gene.
<h6>Obesity</h6>
Unlike other studies where genetic markers that influence food preference were found in genes associated with taste receptors on the tongue. These genes are more associated with how people metabolize food. They could offer more insight for researchers studying diabetes, obesity and nutrition.


Writing recently in the <a href="https://www.nytimes.com/2015/01/01/science/gene-linked-to-obesity-hasnt-always-been-a-problem-study-finds.html" target="_blank" rel="noopener noreferrer">New York Times</a>, Carl Zimmer explained how variants in the FTO gene now associated with obesity may have offered an evolutionary advantage. Now, however, with more sedentary lives those variants could be detrimental to people’s health.
23andMe researchers compiled a white paper looking at these and 27 other variants associated with taste preference.
To find out more you can download the paper <a href="https://blog-api.23andme.com/wp-content/uploads/2015/03/5-N8XiOLkGIgydwX_SS-IQ_23-08_Genetic_Associations_With_Traits1.pdf" target="_blank" rel="noopener noreferrer">here</a>.

Salty Or Sweet

We’re feeling a little dizzy trying to keep track of all the coverage 23andMe’s new study on motion sickness received or it might just be this infographic.


The<a href="http://hmg.oxfordjournals.org/content/early/2015/01/26/hmg.ddv028.abstract?keytype=ref&#038;ijkey=2ntxck5YUKc8QSA"> paper</a>, which came out in late January, was the first ever genome-wide association study of the very common condition.
We want to share with you some of the better stories, including coverage in<a href="https://www.fastcompany.com/3042008/feeling-woozy-23andme-releases-first-ever-genome-wide-study-of-motion-sickness"> Fast Company</a>, the<a href="http://www.theatlantic.com/health/archive/2015/02/the-mysterious-science-of-motion-sickness/385469/"> Atlantic</a> and<a href="https://time.com/3695231/23andme-motion-sickness/"> Time</a>. We also wanted to share some of the findings in the study using this fun infographic.
In the study, 23andMe researchers found 35 genetic variants that were significantly associated with motion sickness. Some of those variants, which were identified for the first time, are in or near genes involved in the development of the eye and ear, while other variants appear to be involved in neurological processes and the regulation of glucose and insulin.
The work also confirmed previously known phenotypic associations between motion sickness and other conditions such as migraines, vertigo, and morning sickness as well as postoperative nausea and vomiting.


Note: this post has been altered from the original; the accompanying  graphic has been removed, along with select text.

Feeling Woozy, Motion Sickness Redux

It turns out that whether you like dark chocolate or milk chocolate may have a little bit to do with your genetics. 
<img loading="lazy" decoding="async" class="alignright size-medium wp-image-22200" src="https://blog-api.23andme.com/wp-content/uploads/2015/02/ValentinesDay-300x300.jpg" alt="ValentinesDay" width="300" height="300" srcset="https://blogcms.23andme.com/wp-content/uploads/2015/02/ValentinesDay-300x300.jpg 300w, https://blogcms.23andme.com/wp-content/uploads/2015/02/ValentinesDay-150x150.jpg 150w, https://blogcms.23andme.com/wp-content/uploads/2015/02/ValentinesDay-768x768.jpg 768w, https://blogcms.23andme.com/wp-content/uploads/2015/02/ValentinesDay-1024x1024.jpg 1024w, https://blogcms.23andme.com/wp-content/uploads/2015/02/ValentinesDay-880x880.jpg 880w, https://blogcms.23andme.com/wp-content/uploads/2015/02/ValentinesDay-1180x1180.jpg 1180w, https://blogcms.23andme.com/wp-content/uploads/2015/02/ValentinesDay-271x271.jpg 271w, https://blogcms.23andme.com/wp-content/uploads/2015/02/ValentinesDay-372x372.jpg 372w, https://blogcms.23andme.com/wp-content/uploads/2015/02/ValentinesDay-574x574.jpg 574w, https://blogcms.23andme.com/wp-content/uploads/2015/02/ValentinesDay-980x980.jpg 980w, https://blogcms.23andme.com/wp-content/uploads/2015/02/ValentinesDay.jpg 1200w" sizes="auto, (max-width: 300px) 100vw, 300px" /> 
We know that our bitter and sweet taste perceptions are highly associated with different genetic variants.
A lot of work has focused specifically on bitter taste perception associated with a variant in the <a href="https://blog.23andme.com/articles/tasty-genetics" target="_blank" rel="noopener noreferrer">TAS2R38 gene</a>. Some people have it and some don’t.
About a quarter of 23andMe customers don’t have the bitter taste variant. This makes them more likely to have a taste for hoppy beer, broccoli or dark chocolate. A variant in theTAS2R38 gene enables some to perceive the bitterness of the chemical propylthiouracil, or PROP. Some so-called supertasters not only perceive bitterness but also can discern more saltiness, sweetness and spice. This suggests that there are other genes involved in our food preference.
So of course the TAS2R38 variant doesn’t explain everything. While surveys of in the United States show that more than half of Americans prefer milk chocolate to dark, among 23andMe customers dark chocolate wins out. Almost half of 23andMe customers prefer dark chocolate. About 39 percent say they like milk chocolate. That may have to do with genetics, but it is more likely related to a mix of other non-genetic factors.
And there are plenty of genetic factors that researchers are still exploring. For instance, a genome wide association study done last year <a href="http://www.newscientist.com/article/dn25672-unravelling-taste-genes-could-help-us-eat-healthily.html#.VN454cYiQih" target="_blank" rel="noopener noreferrer">found 17 genes</a> related to liking certain foods. Thos foods include among other things dark chocolate, blue cheese and liver. These genes belong to the groups of genes that apparently have nothing to do with taste or smell perception.
All this just goes to show that, like love, our food preferences are complicated.

Chocolate, It’s Complicated

Scientists haven’t agreed on whether blondes indeed have more fun, but at least there is some consensus on what makes their hair blond.<img loading="lazy" decoding="async" class="alignright size-medium wp-image-22160" src="https://blog-api.23andme.com/wp-content/uploads/2015/01/Blond-Hair-270x300.png" alt="Blond Hair" width="270" height="300" srcset="https://blogcms.23andme.com/wp-content/uploads/2015/01/Blond-Hair-270x300.png 270w, https://blogcms.23andme.com/wp-content/uploads/2015/01/Blond-Hair.png 287w" sizes="auto, (max-width: 270px) 100vw, 270px" />


23andMe scientists looking at the biology behind hair color found three genetic variants already known to be strongly associated with having golden locks among 23andMe customers with Northern European ancestry.
The three variants are on or near the genes HERC2, KITLG and SLC24A4. 

<h6>Known Associations</h6>

These findings among 23andMe customers confirm<a href="https://www.nature.com/ng/journal/v39/n12/full/ng.2007.13.html"> known associations</a> reported on in several other published studies over the last few years.
Hair color is a complex trait, meaning more than one genetic variant influences whether a person has light or dark hair. And these three genetic variants by no means account for all the genetic factors that influence hair color. But at least for people with Northern European ancestry they explain a lot.


A pigment molecule called melanin determines the color of your hair. People with higher levels of the brown-black form of melanin have darker hair. But people with the lower levels have lighter hair. About 20 percent of 23andMe customers report having light or dark blond hair.

<h6>Why is this important?</h6>

While blond hair is most common in people of Northern European ancestry, it is also found in people without European ancestry. But the biology behind blond hair in those populations is different. For example, between five to ten percent of<a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3481182/"> Solomon Islanders </a>have blond hair that is caused by a single variant in the TYRP1 gene.


Why is it even important to study these kinds of traits you might ask?

Part of the reason researchers look at traits like hair and eye color, is because it provides a broader insight into the biology of complex traits. The color of your hair is not as simple as many might think. For instance, simply having one or two blond hair alleles does not mean that you will have blond hair. In fact, most people with just two blond hair variants don’t have blond hair. Only in people with five or more blond hair alleles do we see a majority of them with light hair.
<h6>Complex Traits</h6>
By studying complex traits like hair color scientists can sometimes gain better understanding about the genetics of other conditions.
Just looking at research about blond hair, for example, has informed scientists about the finely tuned process of gene expression.
<a href="https://www.nature.com/ng/journal/v46/n7/full/ng.2991.html">A 2014 study</a> led by researchers at Stanford looked specifically at the variant nearby, but not in the KITLG gene. The study was fascinating because the researchers showed that  a variant in so-called &#8220;junk&#8221; DNA has a strong influence on the expression of KITLG. This in turn influences hair color. Instead of simply turning on or off expression of the KITLG gene, this variant dialed down the gene expression levels, changing the hair color along a blond to brown gradient.
<div id="attachment_22180" style="width: 650px" class="wp-caption aligncenter"><img loading="lazy" decoding="async" aria-describedby="caption-attachment-22180" class="size-large wp-image-22180" src="https://blog-api.23andme.com/wp-content/uploads/2015/02/blond_hair_snps-640x196.jpg" alt="The frequencies of three genetic variants associated with blond hair across Eurasia. " width="640" height="196" />The frequencies of three genetic variants associated with blond hair across Eurasia.</div>

Blonde on Blonder

So where did that red hair come from? 
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</code>by Kasia Bryc, 23andMe Population Geneticist 
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</code>Most people who see my unruly wild <img loading="lazy" decoding="async" class="alignright wp-image-21956 size-medium" src="http://35.88.189.111/wp-content/uploads/2014/11/Kasia1-197x300.jpg" alt="" width="197" height="300" srcset="https://blogcms.23andme.com/wp-content/uploads/2014/11/Kasia1-197x300.jpg 197w, https://blogcms.23andme.com/wp-content/uploads/2014/11/Kasia1.jpg 369w" sizes="auto, (max-width: 197px) 100vw, 197px" /> 
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As a first generation immigrant from Poland, I don’t have any ancestors from Ireland.
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<h2>Recessive Trait</h2>
Yes, really, just take a look at my 23andMe Ancestry Composition results.
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Yet it is true that red hair is strongly tied to Ireland. Over 10 percent of 23andMe customers of Irish heritage, whose four grandparents were born in Ireland, have red hair. In most other parts of continental Europe, red hair is less common, and its frequency tends to hover between one and three percent. 
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</code>For me, my red hair holds special significance. Both my parents had brown hair, yet both my brother and I have red hair, thanks to the joys of recessive inheritance (No, we’re not adopted. And yes, our family relationships have been confirmed genetically through 23andMe). 
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</code>Red hair acts, for the most part, like a recessive trait, meaning that you need two copies of the red-hair genetic variant to see red hair. Which explains why my parents, each carrying one copy of the variant, didn’t have red hair, but could pass it on to their children by chance, which they did, twice. 
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As a child I puzzled over my hair color – it seemed rather poor camouflage, and surely ill-adapted – how could a trait as odd as red hair have come to be? 
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</code>That early fascination with human traits and evolution helped lead me to a career as a population geneticist. Nowadays I love wrangling with just such questions as I study the genetics of people across the globe. 
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</code>To dive into the genetics of red hair, we first have to understand the function of a gene called the Melanocortin 1 Receptor (MC1R). MC1R acts as a lever that toggles the cells to produce a brown or black pigment instead of producing a reddish yellow pigment. The color of the pigment, and how much is produced, leads to much of the diversity in appearance of humans around the world.
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Genetic mutations can change the normal function of MC1R, leading to a loss of function. That means that the protein the gene makes is changed so much that it doesn’t work as it should. So the pigment-producing cells don’t get their signal to make black-brown pigment that is so protective against the sun’s harmful UV rays,and instead produce more reddish yellow pigment, which, in your hair, gives it a red color.
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About 90 percent of 23andMe customers who report having red hair carry at least one of three of the most common genetic variants associated with red hair variants. Though there are other known and unknown variants involved in determining human pigmentation.
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<h2 class="tablepress-table-name tablepress-table-name-id-1">Do you carry one of these variants associated with red hair?</h2>
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<td class="column-1">R151C</td>
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Three variants highly associated with red hair among 23andMe customers. Not yet a customer? Visit our store!
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</code>For a long time, red hair was thought to be an adaptive trait. Not the hair color itself, but rather, red hair and lighter skin pigmentation are a bit of a package deal, and this lighter pigmentation was thought to be adaptive in northern Europe. Lighter skin color allows the skin to produce sufficient vitamin D when levels of light are low, when you don’t get sufficient levels of the vitamin through your food (such as from fish). So if you were a farmer in, say, Ireland, lighter skin would help you keep your vitamin D levels sufficiently high.
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However, there has been a surprising dearth of evidence for positive selection of red hair in Europeans, and there seems to be no association between red hair and the evolution of light skin in European populations. In contrast, the gene SLC24A5, which is involved with skin pigmentation, has a strong signal of selection. So it seems that for red hair, the vitamin D hypothesis isn’t really substantiated by science. 
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</code>Instead, the current theory most evolutionary scientists believe suggests that selective pressure to maintain proper protective black-brown pigmentation is highly constrained in regions closer to the equator that have strong sun exposure. The production of black-brown pigment, necessitating a functioning MC1R gene, helps shield cells from ultraviolet radiation that can increase the risk of skin cancer. 
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</code>In the far north, it seems, that selection may be relaxed. Comparing the human MC1R gene sequence to a chimpanzee’s genome suggests there was a lot of functional constraint on this gene&#8230; right up until humans migrated out of Africa. Mutations in MC1R that take away production of black-brown pigment may matter less where the sunlight isn’t as powerful. As a result, we observe these mutations, and the accompanying red hair. Sometimes, the mutations drift up in frequency by chance, and red hair becomes (more) common. 
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</code>For an even more nuanced contemplation of skin pigmentation and adaptation, and its possible relationship to the switch from hunter-gatherer lifestyles to farming, check out this read.
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<img loading="lazy" decoding="async" class="aligncenter wp-image-22143 size-larger" src="http://35.88.189.111/wp-content/uploads/2015/01/Red_hair_map-880x350.jpg" alt="" width="880" height="350" srcset="https://blogcms.23andme.com/wp-content/uploads/2015/01/Red_hair_map-880x350.jpg 880w, https://blogcms.23andme.com/wp-content/uploads/2015/01/Red_hair_map-300x119.jpg 300w, https://blogcms.23andme.com/wp-content/uploads/2015/01/Red_hair_map-768x306.jpg 768w, https://blogcms.23andme.com/wp-content/uploads/2015/01/Red_hair_map-1024x407.jpg 1024w, https://blogcms.23andme.com/wp-content/uploads/2015/01/Red_hair_map-1180x469.jpg 1180w, https://blogcms.23andme.com/wp-content/uploads/2015/01/Red_hair_map.jpg 1272w" sizes="auto, (max-width: 880px) 100vw, 880px" />
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<h2>Where are 23andMe customers with red hair from?</h2>
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</code>A closer look at the three most common red hair variants among 23andMe customers shows that red hair allele frequency in Europe does correlate with distance from the equator. The variant that is most common (and is involved in a third of red hair among 23andMe customers) is R151C. Unsurprisingly, this variant is most common in individuals whose grandparents were born in Ireland and in the UK.
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Over 50 percent of 23andMe redheads carry at least one copy of this variant. Are you one of them?
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The variant D294H is also most frequent in Ireland, but overall it is less prevalent, and found in a limited range: mostly Ireland, the UK, and France, Switzerland, and Belgium.
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Unlike the first two, the variant that I carry, R160W, isn’t most common in Ireland. Instead, it is found at its highest frequencies in Sweden and Lithuania, as well as other parts of Scandinavia, Central and Eastern Europe.
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So what do these maps of variants tell us about why red hair might have come to be?
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Well, there does seem to be a correlation between where the variants lie – each variant is most frequent above the 35th parallel, which suggests that there may really be a relaxed selective constraint on MC1R function this far north of the equator.
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<h2><img loading="lazy" decoding="async" class="alignright size-medium wp-image-22093" src="https://blog-api.23andme.com/wp-content/uploads/2015/01/redhair-world-300x300.jpg" alt="redhair world" width="300" height="300" srcset="https://blogcms.23andme.com/wp-content/uploads/2015/01/redhair-world-300x300.jpg 300w, https://blogcms.23andme.com/wp-content/uploads/2015/01/redhair-world-150x150.jpg 150w, https://blogcms.23andme.com/wp-content/uploads/2015/01/redhair-world-768x768.jpg 768w, https://blogcms.23andme.com/wp-content/uploads/2015/01/redhair-world-880x880.jpg 880w, https://blogcms.23andme.com/wp-content/uploads/2015/01/redhair-world-271x271.jpg 271w, https://blogcms.23andme.com/wp-content/uploads/2015/01/redhair-world-372x372.jpg 372w, https://blogcms.23andme.com/wp-content/uploads/2015/01/redhair-world-574x574.jpg 574w, https://blogcms.23andme.com/wp-content/uploads/2015/01/redhair-world-980x980.jpg 980w, https://blogcms.23andme.com/wp-content/uploads/2015/01/redhair-world.jpg 1000w" sizes="auto, (max-width: 300px) 100vw, 300px" />Research</h2>
In researching traits among 23andMe customers, I learned a lot about red hair. I was amazed at how the genetics of just one trait are so complex. For example, not everyone with two MC1R variants reports having red hair. Isn’t that how recessive traits should work?
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But instead, red hair variants aren’t completely penetrant, meaning they don’t always cause the trait. The variant that I carry, R160W, is especially illustrative: only 50 percent of individuals that carry two copies of this variant have red hair.
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On a personal level, I felt reassured that what I knew about my family’s history was consistent with what I found to be true about red hair. But even more, I realized just how widespread red hair variants are across Europe, especially its northern reaches.
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Kasia Bryc

No, I’m Not Irish

Why some people will have a hangover the morning after they ring in the New Year this year and others won’t, can at least be partially explained by genetics.<img loading="lazy" decoding="async" src="https://blog-api.23andme.com/wp-content/uploads/2014/12/Wine-bottle-300x199.jpg" alt="Wine bottle" class="alignright size-medium wp-image-22045" width="300" height="199" />
There’s a lot of variability in how people respond to drinking. A lucky few, about 20 percent, have few symptoms from imbibing too much. But the rest of us pay for a night of indulging with a mix of symptoms that might include a headache, or nausea, or cloudy thinking or all of the above.
<a href="http://www.theguardian.com/science/sifting-the-evidence/2014/dec/12/hangover-severity-genetic-alcohol-inherited" target="_blank" rel="noopener noreferrer">Two studies</a> published earlier this year looked at those differences. Researchers in both studies examined data from twin studies and found that genetics explains about half the “heritability” of hangovers.
Scientists look at heritability to try gauge how variation of a certain trait or condition within a population can be explained by genetics versus how much can be explained by environmental influences. The proportion of variation within a population that’s explained by genetics is known as heritability. 
In this case, the heritability of hangovers is about 50 percent. In other words about 50 percent of the differences between those who have a hangover and those who don’t is explained by genetics. Using identical and fraternal twins allows researchers to isolate environmental and genetic influences.
Unlike <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2442454/" target="_blank" rel="noopener noreferrer">other studies</a> that have looked at specific genetic variants involved in how individuals respond to alcohol or variants that influence the risk for <a href="https://www.ncbi.nlm.nih.gov/pubmed/25439982" target="_blank" rel="noopener noreferrer">alcohol dependence</a>, these studies tried to ascertain how much of the differences in how people respond to a night of drinking is influenced by genetics versus how much is influenced by environmental factors.
In one study that looked at data that was first compiled in the early 1970s among about 13,000 adult male twins living in Australia. The researchers again looked at the data that included information about alcohol consumption, intoxication and hangovers. The other study also looked at data from about 4,500 twins, both men and women, and found that genetics accounted for 45 percent of the difference in hangovers.

Health + Traits — Page 23