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Famous DNA Review, Part II – Genghis Khan

In 2003, researchers from around the world released a paper that suggested that 8% of all Mongolian males have a common Y chromosome because they are the descendants of Genghis Khan (See “The Genetic Legacy of the Mongols,” 2003, Zerjal, et. al., American Journal of Human Genetics, 72: 717-721).The researchers examined the Y chromosome variability of over 2000 people from different regions in Asia and discovered a grouping of closely related lines.The cluster is believed to have originated about 1,000 years ago in Mongolia and its distribution coincides with the boundaries of the Mongol Empire.

Genghis Khan’s empire (he ruled from 1206 – 1227) stretched across Asia from the Pacific Ocean to the Caspian Sea and was reportedly extremely prolific.Khan’s son Tushi had as many as 40 sons.His grandson Kublai Khan is reported to have had as many as 22 sons, and perhaps many more.Together this family may have as many as 16 million descendants alive in Asia today.It is extremely important to note that until DNA can be extracted from Khan’s bones (which have never been found), there is no definitive proof that this Y chromosome cluster is actually descended from Genghis Khan.

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Famous DNA Review, Part I – Thomas Jefferson

Thomas Jefferson, 3rd President of the United States, has been at the center of a DNA controversy for over 200 years.In September 1802 journalist James T. Callender wrote in Richmond Reporter that Jefferson had for many years “kept, as his concubine, one of his slaves.Her name is Sally [Hemmings].The name of her eldest son is Tom.His features are said to bear a striking though sable resemblance to those of the president himself.”Although these rumors had reportedly already been passed around quietly, this article spread the rumor far and wide, setting off many years of debate.

In 1998 analysis of a male descendant of Jefferson’s paternal uncle showed that Jefferson’ Y chromosome belonged to haplogroup K2 (Thomas Jefferson did not have any male descendants to provide DNA.For more information, see: “Jefferson fathered slave’s last child.” 1998. Nature 396 (6706): 27–28. PMID 9817200).Haplogroup K2 is rather rare, constituting just 1% of worldwide Y chromosomes (See “Thomas Jefferson’s Y chromosome belongs to a rare European lineage.” Am J Phys Anthropol 132(4): 584-9.PMID 17274013 ).Surprisingly, or perhaps not-so-surprisingly depending on which side of the debate you stood, a male descendant of Sally named Easton Hemmings possessed the same K2 chromosome, suggesting a genetic link between Jefferson and Easton.Keep in mind, however, that this is not determinative since it is possible that any of Jefferson’s male relatives (who possessed the same Y chromosome) could have fathered Easton.And keeping in mind that non-paternal events are ALWAYS a possibility, nothing is 100% certain.Not until we can time-travel and obtain DNA samples from the source!

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Are aboriginal Australians and New Guineans the modern-day descendants of the extinct species Homo erectus?

Some scientists have hypothesized that Australian aboriginals received a portion of their DNA from an ancient hominid species called Homo erectus, which for a short time was contemporaneous with modern man. A recent study published in PNAS (Proceedings of the National Academy of the Sciences) set out to answer this question by analyzing mtDNA and Y-chromosome samples from aboriginals.

A total of 172 mtDNA and 522 Y-chromosome previously published and new sequences from aboriginal Australians and New Guineans were analyzed for mtDNA and Y-chromosome variation and were compared to the current world haplogroup tree. All of the mtDNA sequences were members of the M and N founder branches, and all of the Y-chromosome sequences fell into the C and F founder branches.

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Genetic Genealogy in Iceland

Yesterday Science published a report from deCODE genetics in Iceland and a second report from academic colleagues in the United States and Canada that announced the discovery of a gene variant (a SNP) on chromosome 9p21 that results in an increased risk of heart attack (the abstracts are available online here and here). The SNP was discovered through genome-wide SNP analysis in Iceland and replicated in three groups of European descent in the United States. I don’t have access to either paper, but according to deCODE’s press release the variant is estimated to account for 20% of the incidence of heart attacks in Europeans, including one-third of early-onset cases (men and women age 50 to 60). Both companies used SNP Chips (that’s fun to say outloud), tiny gene chips that contain thousands and thousands of SNPs across the entire genome. Want to learn more about SNPs? Go to the SNP information page at the Human Genome Project.

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Faces of Britain

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In 2005 the Wellcome Trust established a £2.3 million project (roughly 4.5 million USD) at the University Oxford to examine the genetic makeup of the United Kingdom.The project would be led by the renowned geneticist and Oxford Professor Sir Walter Bodmer, joined by Oxford Professor Peter Donnelly (a population genetics and statistics expert) and the Wellcome Trust Principal Research Fellow Professor Lon Cardon.

The goal of the project is to establish a knowledge base for analyzing genes that are linked to disease.To do this, the researchers hoped to gather DNA from 3000 to 3500 volunteers throughout the UK who live in the same area as their parents and grandparents.Each volunteer’s DNA will be tested for 2000 SNPs (single nucleotide polymorphisms).The data will be combined with each volunteer’s medical history in the attempt to find a link between genetic make-up and the inheritability or susceptibility of a number of diseases such as diabetes and Alzheimer’s.The data will also be used to isolate DNA sequences that characterize the founders of each region of the UK, be they Viking, Saxon, or Celt.

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Recent Genetic Genealogy News

Here are some recent news articles that mention the use of genetics in traditional genealogy:

  1. Internet databases, DNA testing make genealogy an easy pursuit – but only for some – An Associated Press story about the use of DNA testing for people researching genealogy in countries (such as Asia, Africa, etc…) with few online databases.
  2. Genes in fashion – The anthropology department of the California State University has tested the DNA of hundreds of students to create an exhibit called “Immigrants All! Our Migration Tales and Genetic Trails” in the department’s museum.
  3. To Whom Else Does Your DNA Belong? – A response to reporter Amy Harmon’s recent story in the New York Times.Although I don’t agree with the strict opposition voiced in this student article, the title is very similar to the title I chose for my own response.
  4. McCoy tempers in famed feud may have genetic cause – Many of the McCoy’s, one of America’s most famous feuding families, have a genetically inherited disease caused Von Hippel-Landau which cause tumors of the adrenal gland.This can lead to high blood pressure and hot tempers.It turns out that geneticists have been studying and publishing about the family for over 30 years and have traced the disease through at least 4 generations.
  5. Rogue-gene discovery could end family’s tragedy – Another story about using genetics and genealogy to trace the distribution of a devastating mutant gene through a family.This gene, which triggers stomach cancer, has ravaged at least 5 generations of a family in New Zealand.

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Who Crossed the Bering Land Bridge?

dna2.jpgHow many founding Asian groups braved their way across the Bering land bridge during those frigid Pleistocene ice ages?Was it a single wave of people who later developed into the three distinct linguistic and cultural groups that populated the Americas, or were there multiple waves of people each with their own language and culture? Or was it some mix of the two?The issue has been and continues to be a topic of debate.

Linguistic studies of the Na-dene, Aleut-Eskimo, and Amerind language groups suggested that there were three waves across the land bridge, one for each language group.Recent genetic research, however, has suggested that there was only a single wave of founding groups into the Americas. (Read a free online review here).

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MITOMAP Publishes an Updated mtDNA Phylogenetic Tree

MITOMAP, the human mitochondrial genome database, has recently published a paper in Nucleic Acids Research (Free Full Text Here) announcing the completion of a full human mtDNA phylogenetic tree.

This tree, available here(pdf) was constructed from 2959 mtDNA coding region sequences (using the rCRS as the reference).In addition to listing mutations and the study that identified each particular sequence, the tree labels each mutation as a substitution mutation, a silent mutation, a tRNA or rRNA mutation, a mutation in the noncoding region, or a pathological mutation.MITOMAP also provides another valuable tool, tables of mtDNA polymorphisms with source information.

The tree will potentially be very useful to both researchers and genetic genealogists by providing a quick and easy way to characterize new sequences.Anyone interested in learning more about their haplogroup or how their haplogroup fits into the human mtDNA tree will find the new mtDNA phylogenetic tree extremely informative.

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New estimates for the arrival of the earliest Native Americans

 

Scientists have analyzed the mitochondrial and Y-chromosomal DNA from a 10,300-year-old human remains found in On Your Knees Cave on Prince of Wales Island in Alaska.These remains, the oldest human remains known from Alaska or Canada are from a young man in his early twenties.

DNA sequencing showed that the individual’s mitochondrial DNA belongs to an ancient subhaplogroup of haplogroup D that was brought to the Americas rather than mutating from haplogroup D once it arrived in the Americas.Interestingly, a sample of almost 3,500 Native Americans revealed that only 1.5% belonged to the same subhaplogroup of D (characterized by 16223T, 16342C, and 16241G).Those that did were found mostly along the Pacific coast of North and South America.

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