Today’s issue of Science contains a new look into the world of genetic genealogy. “The Science and Business of Genetic Ancestry Testing“, led by researchers at the University of Texas at Austin, examines the benefits and drawbacks of genetic genealogy. Here is a table summary of the researcher’s conclusions:
Table from: â€œDeep Roots”â€ at www.utexas.edu/features/2007/ancestry/.
One interesting fact from the article is that the number of people who have purchased genetic genealogy tests is estimated to be over 460,000! If you would like to read more about this study, there are a number of other sources of information, including a press release from The University of Texas at Austin, where the first author, Deborah A. Bolnick, is assistant professor of anthropology. There is also a feature story at The University of Texas’ website. In this feature story, Dr. Bolnick states:
There is so much information about genetic genealogy in the news right now that I am having a hard time keeping up. That, of course, is good news. So here is a round-up of some of the best from the web:
“Seeking Columbus’s Origins, With a Swab” is an article in today’s New York Times (HT: Liz). Scientists and genetic genealogists hope to use Y-DNA to compare DNA that might be Columbus’s to modern-day people with a related surname.
“Genetic Genealogy Mildly Hot” is a post by Hsien at Eye On DNA that explains why “family tree dna” was one of the top 100 searches at Google Trends yesterday. Got a guess?
In “60 Minutes on DNA: Deja Vu All Over Again“, Megan Smolenyak looks at Sunday’s 60 Minutes segment about genetic genealogy. It’s a brilliant post, especially with the following sentence:
Wow, what a day for personal genetics. Yesterday, J. Craig Venter’s diploid genome was released (I’m not sure where the sequence is, but the paper is available at PLoS Biology, a OPEN ACCESS journal!).
I know that many people have their gripe about Venter, but seeing a story about personal genetics on the front page of CNN is important. It educates people and helps alleviate fears about genomic sequencing. I think it’s a great opportunity for the field. Here’s a few quotes from the CNN story:
“Venter has just published almost all 6 billion letters, or 96 percent, of his own personal genetic code in the journal PLoS Biology. From diseases to personality traits, it’s the most comprehensive human genome to date. Venter’s gene map provides a new understanding of his genetic destiny, according to the DNA inherited from both his father and his mother.
Itâ€™s always been my belief that personal genetics (inexpensive whole-genome analysis) will bring about some exciting changes in the field of genetic genealogy.One of the biggest areas of change will undoubtedly be in the area of autosomal genetic testing.(Remember that autosomal testing examines nuclear DNA, which is DNA other than mtDNA, Y-DNA, or X chromsomes).
A new study takes one of the first steps in the genetic genealogy revolution by examining SNP variations in four self-identified American populations â€“ European, Latino/Hispanic, Asian, and African American (see reference below).â€œThese population labels were used, despite the controversy surrounding the correspondence between notions of race and population structure inferred from explicit genetic data, because they are the labels used by NIH, FDA, and many, if not most, biomedical researchers.â€The researchers sequenced the exons and flanking regions of 3,873 genes from 76 unrelated individuals.
I recently came across a review article by Henry T. Greely, a Professor of Law, Professor (by courtesy) of Genetics, and Director of the Center for Law and Bioethics at Stanford.The article is entitled â€œThe Uneasy Ethical and Legal Underpinnings of Large-Scale Genomic Biobanks (pdf)â€ and was recently published in the Annual Review of Genomics and Human Genetics.
According to Mr. Greely, the identity of participants in large-scale genomic biobanks cannot effectively protected.A biobank is defined as a database of genotypic and phenotypic data.Using genetic information, physical information, or a combination of the two, people can identify an individual in such a large database:
â€œSomeone really interested could get a DNA sample from me – from a licked stamp, a drinking glass, or some tissue – and have it genotyped for a few hundred dollars, but few will have to go to the genomic data; the phenotypic and demographic data will often be sufficient.â€
There is a certain occurrence in genetic genealogy called a Non-Paternal or Non Paternity Event.This is a break in the ancestry of a personâ€™s Y chromosome and surname.A person named â€œSmith,â€ for instance, might have a Y chromosome that is clearly â€œJohnson.â€
A non paternal event can occur when an adopted male takes the surname of his adoptive family, or a male child takes his step-fatherâ€™s surname, or a male child takes his motherâ€™s surname (undoubtedly there are other circumstances as well).
When a break in the Y chromosome is suspected or confirmed, it is possible that the break might have occurred 1,000 years ago, 100 years ago, or with the testeeâ€™s birth.
I am a genetic genealogist because I thought it would be a fun and interesting thing to do.Some people, however, are genetic genealogists because it is a matter of life and death.
The Amish/Mennonites and Genetic Disorders
The Amish migrated from Europe (Germany/Switzerland) to the United States in the 1700s.One such group, the Old Order Amish of Lancaster County, Pennsylvania, began with 200 Swiss immigrants.Today, there are roughly 200,000 Old Order Amish.Because of the difficult lifestyle, the lack of evangelism, and the language barrier, there is essentially no conversion to the Amish religion.In addition, marriage outside the community is forbidden.As a result, the community has remained closed for over 10 generations and is still using the same 200 genomes of their founders!This is known as founder effect, which means that a population is started by just a small number of individuals and as a result that new population will be different (both genetically and phenotypically) from the parent population, potentially with low genetic variation.
The Forbes Series â€“ Forbes has an excellent series of articles relating to genomic sequencing and genetic genealogy.It is well-timed and full of interesting things to think about.I highly recommend reading them all!
1. Will You Get Cancer?
2. The Telltale Tumor
3. Never Mind You â€“ What About Me?
4. Genes of the Rich and Famous
5. Genealogy Gets Genetic
6. 12 Genes That Could Change Your Life
â€œGenome of DNA Pioneer is Decipheredâ€-This is a write-up by Nicholas Wade in the New York Times.Unfortunately, Mr, Wade used the word â€˜decipheredâ€™ in the article rather than â€˜sequencedâ€™.Iâ€™m not convinced that this was his choice, but heâ€™s getting some flack for it.In any event, it appears that Watsonâ€™s sequence took 2 DVDs rather than just one!Â There’s a write-up at Nature News as well.
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 â€œThe Genetic Legacy of the Mongols,â€ 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 Khanâ€™s empire (he ruled from 1206 â€“ 1227) stretched across Asia from the Pacific Ocean to the Caspian Sea and was reportedly extremely prolific.Khanâ€™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 Khanâ€™s bones (which have never been found), there is no definitive proof that this Y chromosome cluster is actually descended from Genghis Khan.
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.