<img loading="lazy" decoding="async" class="alignright size-full wp-image-4273" title="blooddonation" src="https://blog-api.23andme.com/wp-content/uploads/2009/08/blooddonation.jpg" alt="blooddonation" width="350" height="232" srcset="https://blogcms.23andme.com/wp-content/uploads/2009/08/blooddonation.jpg 350w, https://blogcms.23andme.com/wp-content/uploads/2009/08/blooddonation-300x199.jpg 300w" sizes="auto, (max-width: 350px) 100vw, 350px" />
Editor&#8217;s note: This post has been edited to reflect the current product. 
When it comes to blood transfusions, what&#8217;s good for one person might be deadly for another.
This might seem obvious today, but until 1900 the idea of &#8220;blood types&#8221; wasn’t understood. A person in need of a transfusion could find himself getting a donation from just about anyone, and sometimes even an animal!
But in 1900 Austrian scientist <a href="http://nobelprize.org/nobel_prizes/medicine/laureates/1930/" target="_blank" rel="noopener noreferrer">Karl Landsteiner</a> noticed that when the blood of different people was mixed together the cells would often clump up, a process he correctly attributed to an immune reaction between the two blood samples. By the next year he had used this clumping reaction to define three main types of blood, which he named A, B and O. (The fourth blood type, AB, was identified in 1902 by two other scientists, Decastello and Struli.)

After hundreds of years of performing blood transfusions unguided, scientists finally had what they needed to safely transfer blood between people. In 1907, the first blood transfusion utilizing the new typing techniques was successfully carried out, and by World War I transfusions were being performed safely on a large scale.
But knowing what blood to give someone and having it on hand are two different things.
Blood banks are faced with the daunting task of making sure there is enough blood of the right type for everyone who needs it at all times. Blood type O, the &#8220;universal donor,&#8221; tends to be overused. This presents a problem for the approximately 40% of Americans are type O and thus can receive only this type in a transfusion. If supplies run low, their lives could be in danger. At the same time, donated blood with the rare B and AB types can sit unused for so long that it becomes outdated and must be discarded.
One solution to managing the blood supply would be to transform all blood into type O, thus making it suitable for everyone. In the early 1980&#8217;s scientists found a way to do this using an enzyme from coffee beans that could strip certain sugars off of type B blood cells. Clinical trials showed that this method was safe and effective, but the method itself was too time consuming and costly to ever be of clinical use. <a href="http://www.bioedonline.org/news/news.cfm?art=3239" target="_blank" rel="noopener noreferrer">New research, however, has identified bacterial enzymes</a> that can carry out this same process more efficiently. Research with this new method is still in progress.

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More on ABO Blood Type: The Key to Compatibility

<img loading="lazy" decoding="async" class="alignright size-full wp-image-4118" title="neandertaler_reconst" src="https://blog-api.23andme.com/wp-content/uploads/2009/07/neandertaler_reconst.jpg" alt="neandertaler_reconst" width="300" height="401" srcset="https://blogcms.23andme.com/wp-content/uploads/2009/07/neandertaler_reconst.jpg 300w, https://blogcms.23andme.com/wp-content/uploads/2009/07/neandertaler_reconst-224x300.jpg 224w" sizes="auto, (max-width: 300px) 100vw, 300px" />
The Neanderthals have always held a special place in the field of anthropology. &nbsp; The skeletal remains of our short, stocky evolutionary relatives have been found everywhere from Spain to Iraq.
Their physical likeness to our own species, and the possibility that humans and Neanderthals may have interacted, has long fascinated experts and enthusiastic novices alike. &nbsp; But simply studying their skeletal remains and artifacts seemed to leave more questions than answers.
More than 10 years ago an international team of scientists became the first to extract and analyze ancient DNA (aDNA) from a Neanderthal skeleton. By examining the mitochondrial DNA (mtDNA) – which is more abundant in our cells than our nuclear DNA and therefore more likely to preserve – they found that there were enough genetic differences between this Neanderthal and modern humans to classify the two as separate species.
Since this initial foray into Neanderthal genetics there have been attempts to improve aDNA analysis, with the goal of filling in the gaps that traditional anthropological techniques had been unable to. &nbsp; Earlier this year, scientists at the Max Planck Institute for Evolutionary Anthropology became the first to sequence the entire Neanderthal mitochondrial genome &#8211; no easy feat. &nbsp;Now scientists have taken aDNA analysis to the next level by developing a novel technique to extract it more easily, yielding the most comprehensive and accurate results to date. &nbsp; Along the way, they have uncovered some intriguing clues to the possible fate of the Neanderthals. &nbsp;Their results are reported in the July 17 issue of <a id="rvka" title="Science" href="http://www.sciencemag.org/cgi/content/abstract/325/5938/318" target="_blank" rel="noopener noreferrer">Science</a>.

This new study, also led by Max Planck Institute scientists, centers around a novel method for finding and extracting that elusive aDNA from Neanderthal remains. The study took advantage of a new kind of aDNA extraction process, called Primer Extension Capture (PEC). This technique has many advantages over the others, primarily because it allows the aDNA to be completely isolated from all the other molecular junk &nbsp; that can accumulate over time. This yields highly accurate results with much less effort. So instead of simply using this technique on one Neanderthal individual, they analyzed five.
The remains they chose had been excavated from a variety of locations, from Croatia to Germany to Spain and Russia. &nbsp; Most of the remains were between 35,000 and 40,000 years old, which is very close to when Neanderthals were believed to have disappeared from most of their range. &nbsp; They also examined Neanderthal remains from Russia that dated to between 60,000 and 70,000 years old.
After successfully extracting and analyzing the DNA of these remains, the researchers came to a few startling conclusions. &nbsp; First, the level of genetic diversity among the samples was exceedingly low. &nbsp; In fact, the amount of genetic diversity of the Neanderthal samples was less than one-third the diversity we see in modern humans today. For example, two of the samples &#8212; one from Croatia and the other from Germany &#8212; had identical mtDNA genomes. For two individuals living nearly 1,000 miles apart, this is quite unusual; unless there wasn&#8217;t much variation in mtDNA in the first place.
The authors of this report think this genetic homogeneity means that there were far fewer Neanderthals living in Europe and western Asia than they&#8217;d previously thought. Based on their analysis of the five individuals, the they estimated that the total population size of Neanderthals in Europe 35,000 years ago may have had as few as 3,500 females (because mtDNA is passed down maternally, it cannot be used to estimate male population size).
The authors believe there are two possible explanations for this small population size. &nbsp; The first is that, over the 400,000 year history of Neanderthals, their population may have always been small. &nbsp; After all, for much of their existence they survived harsh ice age conditions, so low population size may have been necessary for survival.
But the authors offer an alternate explanation as well. They think this small population size is the result of long-term population decline, perhaps beginning about 40,000 years ago and continuing until Neanderthals were wiped out. To test their hypothesis, the researchers re-analyzed the Neanderthal mtDNA genomes and found that their protein-encoding genes had evolved much more quickly than those of humans or chimpanzees since the three species split, millions of years ago.
This high rate of evolution, the authors argue, was not present in the older Russian Neanderthal sample. &nbsp; This fact implies a pattern of decline in population size, not a population that had been small from the start. These results support their idea that the Neanderthal numbers were on the decline. &nbsp; Without direct evidence, they can only speculate as to the cause of of their decline, but the scientists believe it may be tied to the arrival of humans in Europe and western Asia about 40,000 years ago.
Today most experts believe the Neanderthals were being out-competed by the incoming humans, who had superior technology and language skills. &nbsp; Over time, the Neanderthals were forced to move to more isolated regions in the mountains of France and Spain. &nbsp; By 30,000 years ago, only a few traces remained. &nbsp; Soon after, they were gone. &nbsp; This study reveals some compelling evidence that humans were in fact responsible &#8211; whether directly or indirectly &#8211; for the demise of the Neanderthals.

Novel Techniques Suggest Neanderthal Populations Dwindled in the Face of Expanding Humans

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It may be you&#8217;ve heard a rumor that males are on the brink of extinction.
Whatever you may think of that prospect, the rumor is false. But over the past decade, numerous <a href="https://www.ncbi.nlm.nih.gov/pubmed/17400006?ordinalpos=1&amp;itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DiscoveryPanel.Pubmed_Discovery_RA&amp;linkpos=1&amp;log$=relatedreviews&amp;logdbfrom=pubmed" target="_blank" rel="noopener">studies</a> have hinted that the Y chromosome, a male necessity, is going the way of the dodo.
Though other studies have suggested this idea may be a bit of an exaggeration, a new report this week suggests that the Y chromosome may indeed be endangered.
In most mammals, such as us humans, two chromosomes determine the sex of each individual organism: &nbsp; the X and the Y. &nbsp; If an individual&#8217;s cells contain two copies of the X chromosome, then they will be genetically female. &nbsp; If they contain one copy of the X and another of the Y, they will be male.

Yet even though these aptly named sex chromosomes have a similar duty – to confer sex – the X and the Y could not be more different. &nbsp; The most striking difference between the two is their size; the Y is less than half as big as the X, and contains only 78 genes, compared to the more than 2,000 found along the X chromosome. &nbsp; The evolutionary history of the two sex chromosomes and the question as to why they are so different from each other has been the subject of heated debate for many years. &nbsp; Now scientists at Pennsylvania State University believe they&#8217;ve found a way to uncover not only the difference between the X and Y, but how and why it arose and what this means for the future of the small, but essential, Y chromosome. &nbsp; Their results are reported in the July 17 issue of <a href="http://www.plosgenetics.org/article/info%3Adoi%2F10.1371%2Fjournal.pgen.1000568" target="_blank" rel="noopener">PLOS Genetics</a>.
The research team, led by biologists Kateryna Makova and Melissa Wilson, believes the key to understanding the origins and future of the Y chromosome lie in some of our most distant mammalian relatives. &nbsp; There are three classes of mammals: egg-layers like the platypus, marsupials like the kangaroo, and the eutherians, which includes humans and thousands of other similar species. &nbsp; While there are many differences between the three groups, one of the most striking is the difference in the organization of the sex chromosomes. &nbsp; As Makova explained, &#8220;In eutherian mammals, the sex chromosomes contain an additional region of DNA whereas, in the marsupials and egg layers, this additional region of DNA [is not on a distinct chromosome, but] is [a region of] the non-sex chromosomes.&#8221;
The authors argue that the key to the origins of the X and the Y chromosomes may lie in this fundamental difference. &nbsp; By analyzing the X and Y of humans compared to the sex-determining regions of marsupials and egg-laying mammals, Makova and Wilson found that the X and Y split from the other chromosomes about 80 to 130 million years ago.
But that is not all they found. &nbsp; The authors also examined how fast the X and Y mutated over time, and noticed a startling change that occurred at about the same time as the split. &nbsp; &#8220;Our research revealed that the Y-specific DNA began to evolve rapidly at the same time that the DNA region split into two entities, while the X-specific DNA maintained the same evolutionary rate as it had previously,&#8221; Makova explained.
In other words, as soon as the X and the Y split their own distinct chromosomes, the Y began to evolve much more quickly than its counterpart, mutating at a much higher rate with each new generation. &nbsp; The faster the Y evolved, the faster its genes disappeared. &nbsp; Whereas at one point the Y may have contained thousands of genes, that number has dwindled to the mere 78.
The disappearance of these genes over time and the small number of those remaining on the Y begs the question: &nbsp; will the Y chromosome ever disappear entirely? &nbsp; The authors believed this was an important question to answer as well, and began additional analysis to determine the fate of the Y.
Makova and Wilson reasoned that there must be some utility to the Y, or else it surely would have disappeared by now. &nbsp; As Wilson states, &#8220;we know that a few of the genes on the Y chromosome are important, such as the ones involved in the formation of sperm &#8230; . &nbsp; Although there is evidence that the Y chromosome is still degrading, some of the surviving genes on the Y chromosome may be essential.&#8221; &nbsp; By performing additional tests, they found that there were indeed some genes on the Y that will probably never disappear entirely. &nbsp; But they also found several genes that were already disappearing, and were likely to be gone many generations from now.
Some recent studies have produced evidence that the genes on the Y may not be disappearing as fast as was initially thought. But, according to Makova, the Y chromosome may not be out of the woods just yet. &#8220;We still think there is a chance that the Y chromosome eventually could disappear,&#8221; she says. &nbsp; &#8220;[But] if this happens, it won&#8217;t be the end of males.&#8221; &nbsp; Instead, she believes that a new pair of sex chromosomes will arise from the genome, latching on to those few remaining genes, keeping alive the genes necessary for male survival.

The Disappearing Y: New Study Uncovers the History and Future of the Y Chromosome

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Most experts agree that the earliest examples of farming and animal domestication lie in the aptly named Fertile Crescent in present-day Iraq.
<h2>Earliest Farming Communities</h2>
But still, many questions have lingered over the years, especially about remnants of farming or animal domestication that have not survived to the present day.   What kind of tools did they use to farm the earliest crops? How did they transport these crops to neighboring communities? Now a new archaeological discovery in the mountains of Turkmenistan has finally given us more answers than questions, and has shed light on some of earliest farming communities in western Asia.
The finds center around discovering several model-sized carts at the archaeological site of Altyndepe, a Bronze Age settlement near Ashgabat in southern Turkmenistan. These tiny carts may have been used in ritual ceremonies or simply been young children&#8217;s toys.   However, the most interesting aspect of these carts is that they depict camels as the main beasts of burden. Archaeologists are always interested in artifacts from ancient civilizations that reveal clues about daily life, and these camel-pulled carts are a comparative jackpot.
<h2>Of Camels and Carts</h2>
An article about the carts recently appeared on the Discovery News website. They were documented by Lyubov Kircho of the Institute for the History of Material Culture at the Russian Academy of Sciences. They are described (in Russian) in the journal Archaeology, Ethnology and Anthropology of Eurasia. An English version will be published in the Proceedings of the 19th International Conference of the European Association of South Asian Archaeologists.
Archaeologists have discovered cattle-pulled carts from the region about 6,000 years ago. These carts were initially used for transporting necessities like grain but later carried other items like alabaster and the prized stone lapis lazuli from hundreds of miles away. Trade networks with neighboring communities began to spring up, and by 3,500 BC, one of the first dedicated &#8216;highways&#8217; for vehicles had been built between Altyndepe and nearby towns in present-day Iran and Afghanistan.
<h2>Influence of Climate</h2>
But by 3,000 BC, the climate was becoming more arid, and the people of Altyndepe could no longer trust their cattle-pulled carts to make the long journeys. Archaeologists already suspected that the communities must have switched to camels, which could handle the drier climate better. Now, these model carts show that their suspicions were correct; camel-pulled carts were the standard for this region and were such an integral part of daily life that miniature versions were created as children&#8217;s toys.
<h2>The Genetic History</h2>
The presence of these carts &#8211; combined with previous ideas on the sharing of ideas and culture throughout this part of Western Asia &#8211; also has implications for the genetic history of the region. It is well documented that about 10% of modern Europeans contain a genetic signature of the early agriculturalists who arrived from the Near East about 9,000 years ago, bringing their farming techniques and DNA.
Scientists now believe that while some of these Near Eastern farmers did travel west into the heart of Europe, others headed into the plateaus and foothills east of the Caspian Sea. Like their Western counterparts, these farmers brought their farming tools and techniques to the indigenous people of southern Turkmenistan. And like their Western counterparts, they probably got their genes. In fact, some genetic studies have examined the genetic makeup of modern-day residents of Turkmenistan and have found that many of these people also bear the genetic signatures of the early farmers of the Fertile Crescent.

Archaeologists Discover Early Example of Domesticated Camels

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Not many people could survive the harsh conditions of the Sahara Desert.   Yet the Tuareg have lived in the the region for millennia.
<h6>Free People</h6>
The Tuareg call themselves the Imazghan, meaning &#8220;free people.&#8221; Today they are known for a distinctive dark blue turban worn by the men, and for their long history as gatekeepers of the Sahara Desert. They are a semi-nomadic people who inhabit the West-Central Sahara, which encompasses parts of western Libya, Algeria, Mali, Niger, and some neighboring countries.
The Tuaregs were first mentioned by the ancient Greek historian Herodotus, who spoke of a group known as the Garamantes living in the Fezzan region of southwest Libya that operated trans-Saharan trade routes, connecting the heart of Africa to the North African coast. It is now believed that he was speaking of the Tuareg.
<h6>Uncovering a mystery with DNA</h6>
Though known to scholars since Herodotus&#8217; depiction thousands of years ago, the Tuaregs remain shrouded in mystery. Their extreme isolation in one of the earth&#8217;s harshest environments has made them difficult for cultural anthropologists to study.   There have been only a handful of studies published on the Tuaregs&#8217; genetic history, and even these examined only the genetics of western Tuaregs from Mali, Niger and Nigeria. The eastern Tuaregs who inhabit the Fezzan of Libya remain far less studied.
So a team of scientists decided to rectify this lack of genetic data, analyzing the mitochondrial DNA (mtDNA) of more than 100 Tuaregs from the Fezzan region of Libya. Their results are reported in the July issue of Annals of Human Genetics.
<h6>A Surprising Haplogroup</h6>
The authors chose to analyze the mtDNA for a variety of reasons, but mostly as a way of comparing their results to the previous genetic studies that had also used mtDNA.
After extracting the DNA of the Tuaregs and assigning each individual to a specific maternal ancestry branch, or haplogroup, they found that the majority of Tuaregs fell into the same haplogroup: H1. In fact, over 61% of the individuals bore haplogroup H1.
This piqued the researchers&#8217; interest, mainly because H1 is often thought to have spread with people from the Iberian peninsula across Europe after the end of the Last Ice Age about 12,000 years ago. The results of this study indicate that somehow H1 must have traveled into North Africa as well.
<h6>Genetic Isolation</h6>
Not only did the researchers find that so many Tuaregs bear the same maternal haplogroup, but there was low genetic diversity among the population overall. This low genetic diversity can be tied to the fact that the Tuaregs are a very isolated people, and it is uncommon for them to venture too far outside their community when looking for a spouse. Indeed it seems that these Libyan Tuaregs are even genetically isolated from their West African counterparts, who showed far less European ancestry and far more ancestry tracing back to sub-Saharan Africa, despite the fact that both eastern and western Tuaregs share a common language and culture.
The authors have used these bits of information to piece together a scenario for the origins of the Libyan Tuaregs.
<h6>The Tuaregs Origins</h6>
Environmental data reveal that, about 5,000 years ago, the Sahara was quickly shifting from its post-Ice Age period of relative stability and good living conditions to a less stable and more arid environment.
This shift, the authors propose, was responsible for a series of human migrations throughout the Sahara that led different Tuareg groups living in the region to separate.   It caused other Tuareg groups to intermingle with neighboring groups.   Some Tuaregs, like those in Mali, Niger, and Nigeria, probably had more contact with sub-Saharan West Africans, which accounts for the higher percentage of sub-Saharan maternal haplogroups found by previous genetic studies.
Others, like the Libyan Tuaregs analyzed here, may have met and mingled with groups such as the Berbers of the Mediterranean coast of North Africa.   Apparently migrations from Spain after the Last Ice Age, across the Strait of Gibraltar into Morocco, brought H1 into the African continent. It then made its way into the North African Berber populations, eventually finding its way into the Libayan Tuaregs.
And what of the 35% of Libyan Tuaregs with sub-Saharan African genetic ancestry?   The authors of this study believe this to be a genetic signature of the trans-Saharan slave trade, which the Libyan Tuaregs famously operated during the 1st century BC, and which brought them to the attention of Herodotus so many years ago.

People of the Veil: New Study Reveals Clues to Origins of the Nomadic Tuaregs

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DNA Day was created in 2003 by a congressional resolution to celebrate two important milestones in the study of genetics: the 50th anniversary of the description of the double-helix structure of DNA by James D. Watson and Francis H.C. Crick and the completion of the Human Genome Project. DNA Day is usually celebrated on April 25th, but to accommodate classroom schedules, many activities will be taking place a day early on Friday April 24th.
<ul>
<li>DNA Day Chatroom: The National Human Genome Research Institute (NHGRI) will be hosting its annual <a href="https://www.genome.gov/20519689" target="_blank" rel="noopener noreferrer">DNA Day chatroom</a> from 8 a.m. to 6 p.m., EDT on April 24th. Genomics and genetics experts will answer questions from students, teachers and the general public on topics ranging from basic genomic research to the genetic basis of disease to ethical questions about genetic privacy. Transcripts from past chatrooms can be found <a href="https://www.genome.gov/20519689" target="_blank" rel="noopener noreferrer">here</a>.</li>
<li>Teaching Tools for DNA Day: To plan your own DNA Day activities, check out the NHGRI’s collection of <a href="https://www.genome.gov/20519692" target="_blank" rel="noopener noreferrer">teaching tools</a> and webcasts. &nbsp; And don&#8217;t miss our collection of DNA-themed activities.</li>
<li>DNA Day Online: National DNA Day is on Facebook and Twitter. &nbsp; You can compete to win a NHGRI mug in their DNA model photo contest. &nbsp; Pictures can be uploaded through April 24th. &nbsp; You can also send a virtual gene via Facebook (thanks to <a href="https://blog.23andme.com/2008/05/02/giving-the-gift-of-a-virtual-gene/" target="_blank" rel="noopener noreferrer">Genome Alberta</a>) or send a DNA Day e-card.</li>
</ul>
What are you doing to celebrate? &nbsp; Leave us a comment — we’d love to know. &nbsp; And if you know of any cool DNA Day happenings, let us know about those too!

DNA Day 2009 — It’s Almost Here!

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How can geneticists tell when a genetic difference between two human populations is an accident and when it’s the result of natural selection?
As our species moved out of Africa and spread out across the globe, there were a lot of chances for random DNA mutations to occur.   Many of these were neutral — they didn’t help or hurt a person’s chances for survival or reproduction — and whether they stuck around in a population’s gene pool was just a matter of luck. But some of these mutations actually helped people deal with the environmental changes and challenges they were facing.   These advantageous mutations tended to build up in frequency over the generations as they enhanced the reproductive success of the people who inherited them.
In some cases, there’s a satisfyingly simple story that demonstrates how a random mutation led to an advantage.   The version of the lactase gene that confers lactose tolerance, for example, is much more common in people of European ancestry than those with African or Asian ancestry.   This fits with the fact that about 8,000 years ago some of the world’s first dairy farmers emerged in — you guessed it — Europe.   For these people, the ability to digest milk would clearly have been a boon.
But some genetic differences between populations haven’t been so straightforward to explain. For example, one version of a variation in the p53 gene is found at higher levels in people with European ancestry than in those with African ancestry.   Is this just a matter of chance, or was there a reason this version of the gene increased in frequency as people moved north?
The best guess scientists have had so far is that the genetic difference has something to do with latitude and, by extension, exposure to UV radiation from the sun.   It’s certainly a plausible explanation.   The p53 gene helps protect cells from cancer, and UV radiation is known to be mutagenic.   But almost any difference between European and African populations would correlate with latitude, so that doesn’t prove anything.
In a study published online last week in the American Journal of Human Genetics, a group of researchers analyzed this p53 variation in Asian populations that are closely related genetically (at least compared to European vs. African populations), but nonetheless live at very different latitudes.   Their results were somewhat surprising.   The p53 variation does vary with latitude, but it’s not correlated with UV radiation level.   Instead, it’s how cold it gets in the winter that seems to matter.
Researchers analyzed rs1042522 in 4,029 people from 67 populations located throughout eastern Asia, from 11 ° south of the equator (Indonesia) to 65 ° north (northern China). They found that the C version of this SNP is more common at higher latitudes, as was expected based on the work in European and African populations.
The amount of UV radiation a locale receives, however, showed no correlation with the frequency of the C version of the SNP.   Instead, it was chillier winter temperatures that seemed to translate into more people in the population having the C version of rs1042522.
<img loading="lazy" decoding="async" class="size-full wp-image-3306 alignright" title="rs1042522" src="https://blog-api.23andme.com/wp-content/uploads/2009/04/rs1042522.jpg" alt="" width="355" height="253" srcset="https://blogcms.23andme.com/wp-content/uploads/2009/04/rs1042522.jpg 921w, https://blogcms.23andme.com/wp-content/uploads/2009/04/rs1042522-300x215.jpg 300w, https://blogcms.23andme.com/wp-content/uploads/2009/04/rs1042522-768x550.jpg 768w" sizes="auto, (max-width: 355px) 100vw, 355px" />
But why would the C version of rs1042522 be advantageous in colder climates?   Like so many genetic adaptations, it may all come down to making babies.
Using previous research about p53 as their guide, the authors of the study tested the ability of different forms of the p53 gene — containing either a C or a G at rs1042522 — to activate LIF, a gene important for embryo implantation in the womb, at different temperatures.
The results of these experiments indicate that the C version of the p53 gene is better at activating LIF in the cold.   This suggests that as populations moved into colder climates, those people with the C version of rs1042522 might have had an easier time conceiving (and therefore would have left behind more offspring, who in turn would pass the C version of the SNP on to their children).
But can a colder climate really bring down conception rates?   The parents of “<a href="http://www.cnn.com/2007/LIVING/wayoflife/09/27/blizzard.babies/index.html" target="_blank" rel="noopener noreferrer">blizzard babies</a>” might disagree, but the authors point out that in cattle at least, cold temperatures have been shown to have an effect.
Bonus: 
The researchers also looked at rs2279744, a variation in the MDM2 gene that (like rs1042522 in p53) is found at different frequencies in different populations.   The MDM2 variation did not vary with latitude or temperature, but did correlate with UV radiation levels.   Populations with higher UV radiation exposures had higher frequencies of the G version of rs2279744.
The MDM2 gene encodes a protein that reduces cellular levels of the p53 tumor suppressor protein. The G version of rs2279744 leads to higher levels of MDM2 protein, and thus lowers levels of p53.   The researchers speculate that as people moved out of Africa and into Asia, the lower levels of DNA-damaging UV light meant they could afford to have less p53 in their cells.   Because lower p53 levels are better for embryonic development, the scientists think nature would have favored the G version of rs2279744.
Bonus Bonus: 
Do p53 and MDM2 sound familiar?   Last week the Blog covered recent reports linking rs1042522 to <a href="https://blog.23andme.com/articles/snpwatch-genetic-variation-in-tumor-suppressor-may-predict-worse-outcome-for-african-american-colorectal-cancer-patients/" target="_blank" rel="noopener noreferrer">colorectal cancer survival in African Americans</a> and rs2279744 in <a href="https://blog.23andme.com/articles/snpwatch-genetic-variation-may-explain-why-young-women-are-at-greater-risk-for-melanoma-compared-to-young-men/" target="_blank" rel="noopener noreferrer">MDM2 to melanoma risk in young women</a>.
Map of rs1042522 frequencies is from the <a href="http://hgdp.uchicago.edu/" target="_blank" rel="noopener noreferrer">HGDP Selection Browser</a>.

Researchers Tie Variation in Cancer Gene to Winter Temperatures

<img loading="lazy" decoding="async" class="alignright size-full wp-image-3133" title="parkinsonsdisease" src="https://blog-api.23andme.com/wp-content/uploads/2009/03/parkinsonsdisease.jpg" alt="" width="260" height="236" />PET scans showing dopamine activity in a normal brain and a Parkinson&#8217;s patient&#8217;s before and after treatment with a therapeutic implant.
More than a million Americans have Parkinson&#8217;s disease, and another 50,000 are diagnosed each year. Scientists know that many of the characteristic symptoms of Parkinson&#8217;s – tremors, rigid muscles and movement problems – can be traced back to the loss of dopamine-producing brain cells.
But what researchers don&#8217;t fully understand is why these cells are damaged in the first place. There are no clear environmental triggers for Parkinson&#8217;s, and in most people with the disease genetics doesn&#8217;t seem to play a large role either. It could even be that Parkinson&#8217;s is really a number of different diseases, all of which lead to the same end result.
Previous research has ruled out genetics as a major contributor to Parkinson&#8217;s risk; it is estimated to play a role in fewer than 10% of cases. But piecing together the genetics of Parkinson&#8217;s is an active and promising field, because what scientists learn from that minority of cases could improve their understanding of the disease generally. The holy grail would be to pin down all the ways genes can interact with the environment to produce the symptoms of Parkinson&#8217;s.

23andMe is working with the <a href="http://www.michaeljfox.org/" target="_blank" rel="noopener">Michael J. Fox Foundation</a>, the <a href="http://www.thepi.org/" target="_blank" rel="noopener">Parkinson&#8217;s Institute</a> and patients from around the world partly because we want to give individuals with Parkinson&#8217;s access to their own genetic data. At the same time, we want to join the continuing quest for those genetic and environmental factors that underlie Parkinson&#8217;s disease by combining genetic data from our community with members&#8217; responses to surveys about their health.
By far the most common known genetic cause of Parkinson&#8217;s disease is the G2019S mutation, which occurs in a gene called LRRK2. While the average person has a 1-2% chance of developing Parkinson’s, the risk for someone with the G2019S mutation is much higher and increases with age. One recent study found that a person who inherits this mutation from either parent has a 28% chance of developing Parkinson’s by the age of 59, 51% by the age of 69 and 74% by the age of 79.
Even though it is the most common known genetic cause of Parkinson&#8217;s disease, the G2019S mutation is responsible for only a small fraction of all cases worldwide – about one or two in a hundred. But in some ethnic groups it is a much more frequent cause of the condition. According to published research, up to 40% of people of North African Arab ancestry and 20% of Ashkenazi Jewish people with Parkinson’s have this mutation.
Another mutation in the LRRK2 gene, referred to as G2385R, has been associated with Parkinson&#8217;s disease in several East Asian populations. Analyses of the combined results from several studies indicate that people who inherit this mutation from either parent are at two to three times greater odds of developing Parkinson&#8217;s than those who do not carry the mutation. Approximately 9% of Parkinson&#8217;s patients with Asian ancestry carry the G2385R mutation.
(23andMe customers can find out if they carry the LRRK2 G2019S mutation in the Parkinson&#8217;s Disease Clinical Report. Customers can also find out if they carry the G2385R mutation using the Parkinson&#8217;s Disease: Preliminary Research Report.)
Although people who have at least one copy of the LRRK2 G2019S or G2385R mutation have an increased risk of Parkinson’s disease, a substantial proportion of people with these mutations never develop the disease. Very little is known about the function of the protein made by the LRRK2 gene, and no one knows why many people who carry mutations in this gene don’t develop Parkinson’s disease. Adding to the mystery, among those with these mutations who do develop Parkinson&#8217;s, not all have the same symptoms. Interactions of these mutations with unknown environmental factors may be part of the explanation. Continuing research into these gene-environment interactions could yield valuable clues into the causes of Parkinson&#8217;s generally.
Mutations in several other genes have also been associated with Parkinson’s disease, but these are extremely rare. Many have been found only in one or two families. 23andMe is not able to detect most of these rare mutations.
Other Parkinson’s mutations:
<ul>
<li>As is the case for mutations in LRRK2, a person need only inherit a mutation in the alpha-synuclein gene (SNCA, also known as PARK1 or PARK4) from one parent to be at substantial risk for Parkinson&#8217;s disease. The average age for disease onset in people with a disease-causing mutation in this gene is 46. The protein encoded by the alpha-synuclein gene is one of the main components of the protein aggregates found in brain cells of people with Parkinson&#8217;s disease.</li>
<li>Mutations in parkin (PARK2), PINK1 (PARK6) and DJ1 (PARK7) are recessive, which means a person must inherit mutated copies of these genes from both parents in order to develop Parkinson&#8217;s (there are rare exceptions). Multiple mutations in each of these genes have been identified; some are extremely rare.</li>
<li>Parkinson&#8217;s disease caused by mutations in parkin, PINK1 or DJ1 usually strikes at a young age. Parkin mutations most often lead to disease onset between the ages of 20 and 40, although some people are younger than 10 or older than 60 when they develop symptoms. PINK1 mutations usually cause Parkinson&#8217;s between the ages of 32 and 48. DJ1 mutations are associated with an age of onset between 20 and 40 years of age.</li>
</ul>
This is an exciting time in the history of Parkinson&#8217;s research. The genetic aspects of the disease could reveal information that is invaluable in the ongoing search for new treatments, or even a cure. We invite Parkinson&#8217;s patients, their families and friends, and anyone who believes in the power of scientific research to change lives to participate in the 23andMe Parkinson&#8217;s disease community. Visit the 23andMe Parkinson&#8217;s community page to learn more.

Understanding The Genetics of Parkinson’s Disease: A Work In Progress

<img loading="lazy" decoding="async" class="alignright wp-image-3125 size-full" title="nycpeeps2" src="http://35.88.189.111/wp-content/uploads/2009/03/nycpeeps2.jpg" alt="People on a city street waiting to cross." width="453" height="273" srcset="https://blogcms.23andme.com/wp-content/uploads/2009/03/nycpeeps2.jpg 453w, https://blogcms.23andme.com/wp-content/uploads/2009/03/nycpeeps2-300x181.jpg 300w" sizes="auto, (max-width: 453px) 100vw, 453px" />
Before 500 years ago people rarely went far to find a mate, choosing a husband or wife from the locally available pool of men and women. But with the dawn of European colonialism people from different parts of the world were suddenly living side by side, and had a whole new set of people to choose from when picking a mate. This trend continues especially in today&#8217;s world, where education and work opportunities have flung young people across the globe, allowing them to interact &#8211; and potentially marry &#8211; people from opposite sides of the globe.
There is ample historical evidence for an increase in exogamy (that is, marrying someone outside your village or town) over the past few hundred years, but could there be evidence stored in our genes as well?   In this week&#8217;s <a href="http://www.plosgenetics.org/article/info%3Adoi%2F10.1371%2Fjournal.pgen.1000415" target="_blank" rel="noopener">PLoS Genetics</a>, an international team of scientists claims to have found genetic clues that allow them to see decreases in inbreeding across the 20th century.

Every person has two copies of each gene – one from our mother and the other from our father.   The more closely related a person&#8217;s parents are, the more similar those two copies are to one another.
The authors of the PLoS Genetics study examined the DNA of more than 800 Americans of European ancestry who ranged in age from 19 to 99. Then they looked at how closely each person&#8217;s two DNA strands matched one another, a measure called autozygosity that roughly corresponds to the amount of inbreeding in an individual&#8217;s pedigree.
The results overwhelmingly confirmed the notion that levels of autozygosity have significantly decreased over time.   When the authors examined the DNA of the youngest subjects, they found significantly lower levels of autozygosity when compared to the oldest subjects.   In fact, they found a steady decrease in levels as they went from oldest to youngest.
What does this mean?   In the last several generations, there&#8217;s been a steady decrease in marrying someone from the same town, village, or region (who could potentially be a distant relative).   Instead, the percentage of people who&#8217;ve chosen to marry someone from a different town, village, region, or even continent, has been on the rise.
According to the authors there are benefits to this increase in genetic diversity, primarily a reduction in the risk of recessive genetic diseases.

23andMe and You — Page 11