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Tuesday, 6 February 2007, 19:18 GMT DNA clue to presidential puzzle By Paul Rincon Science reporter, BBC News
DNA results from Thomas Jefferson were a mystery
DNA tests carried out on two British men have shed light on a mystery surrounding the ancestry of Thomas Jefferson, America's third president.
In the 1990s, DNA was taken from male relatives of Jefferson to see if he fathered a son with one of his slaves.
They found the president had a rare genetic signature found mainly in the Middle East and Africa, calling into question his claim of Welsh ancestry.
But this DNA type has now been found in two Britons with the Jefferson surname.
Professor Mark Jobling, from the University of Leicester, and colleagues discovered the two British Jeffersons possessed the same rare male (or Y) chromosome type as the third US president.
This unusual lineage has not been found in white Britons before. Last month, Professor Jobling's group reported the discovery of seven white men from Yorkshire carrying a West African Y chromosome.
Welsh extraction
The Y chromosome is a package of genetic material passed down from father to son, more or less unchanged - just like a surname.
Over time, it does accumulate small changes in its DNA sequence, allowing relationships between different male lineages to be studied.
Y chromosomes can be classified into different groups (haplogroups) which, to some extent, reflect a person's geographical ancestry.
Certain haplogroups might be common in, for example, East Asia but rare in Europe. In Britain, sharing a surname raises the likelihood of sharing the same Y chromosome type.
The two men in the Jefferson study had paternal ancestry in Yorkshire and the West Midlands respectively.
Jefferson's haplogroup - and the one he shares with the two men from Britain - is known as K2.
This discovery of K2 in Britain scotches any suggestion that Jefferson - who was US president between 1801 and 1809 - must have had recent paternal ancestors from the Middle East.
Jefferson's Y chromosome was most similar to that of a man from Egypt. But genetic relationships between different K2s are poorly understood, and this may have little significance.
Instead, say the researchers, their study makes Jefferson's claim to be of Welsh extraction much more plausible.
The double-stranded DNA molecule is held together by four chemical components called bases Adenine (A) bonds with thymine (T); cytosine(C) bonds with guanine (G) Groupings of these "letters" form the "code of life"; there are about 2.9 billion base-pairs in the human genome wound into 24 distinct bundles, or chromosomes Written in the DNA are about 20-25,000 genes which human cells use as starting templates to make proteins; these sophisticated molecules build and maintain our bodies
Common ancestor
K2 makes up about 7% of the Y chromosome types found in Somalia, Oman, Egypt and Iraq. It has now been found at low frequencies in France, Spain, Portugal and Britain.
Professor Jobling explained: "Finding that Jefferson's Y chromosome was one mutational step away from an Egyptian type makes you think 'crikey, could he have a relatively recent origin in the Middle East?'
"Our point is that we find, at lower frequencies, French, British and Iberian K2s and they are jolly diverse. His fits into that picture of a west European sub-population of K2."
The DNA sequences of individual K2s - including those from Europe - are quite different from one another.
This "genetic diversity" has to accumulate over time, supporting the idea K2 is not a recent introduction into Europe.
The haplogroup has probably been present for centuries in the "indigenous" population of western Europe, says Professor Jobling, and is not exclusive to the Middle East and Africa.
Paternity case
It could have been introduced to Europe by the Cro-Magnons - the first modern humans to colonise the continent 40,000 years ago. Alternatively, it could have arrived in the Neolithic (8,500-4,500 years ago), brought from the Near East by the first farmers.
Another theory concerns the Phoenicians, an ancient maritime trading culture that spread out across the Mediterranean from their home in what is now Lebanon. K2 is relatively common today in Lebanon, leading to suggestions that European K2s may be descendents of these ancient traders.
In 1998, Jobling and others completed an investigation looking at whether Jefferson, main author of the Declaration of Independence, had fathered a son with Sally Hemings, a slave he owned.
Rumours had long existed that the two had one or more children. Since Jefferson had no surname-bearing progeny, the team used samples from descendents of his paternal uncle as a proxy.
They compared these with descendents of Eston Hemings Jefferson, Sally's last son. The Y chromosomes matched, suggesting that Jefferson, or one of his paternal relatives, was Eston's father.
Details appear in the American Journal of Physical Anthropology.
quote: K2 makes up about 7% of the Y chromosome types found in Somalia, Oman, Egypt and Iraq. It has now been found at low frequencies in France, Spain, Portugal and Britain.
This is a bit confusing, i thought somalia had the distribution (5%) E3a, (15%) J and (80%) E3b of the Y chromosome, so how does this (7%) K2 fit in the picture, is their some new study done from there that includes this K2? Sorry i'm pretty bad on this genetic stuff so bear with me if there is already a thread talking about K2 coz i've never heard of this before.
Posts: 1420 | Registered: May 2005
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Very Interesting, I was wondering has anyone heard about where you can get from National Geographic a kit that you use to swab your mouth, then you send it back to them and they do DNA testing on it to determine where your ancestors came from? I was interested in doing it, this story reminded me of that.
Posts: 1879 | From: Going to Graceland | Registered: Nov 2006
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I am adopted. Back in the late 60's there was a lot of hiding stuff. A lot of privacy, secrecy, etc. I have looked into my birth records. There is absolutely nothing there. So without a lot of money and time, which I don't have. I had given up hope of finding out "what blood" I have. Not that it's a big deal. I could live without knowing. But, to have a chance to know, am I; Scottish, Arab, Italian, Russian, etc.....well that would be nice. Would be cool for my kids to know too.
For $200, I could find out. That's really cool. Thanks for posting this.
-------------------- شكرا و أللام عليكم شيبى Posts: 2133 | From: Redneckland | Registered: Oct 2006
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UBBFriend: Email this page to someone!
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Would be cool for my kids to know too. ![[Big Grin]](biggrin.gif)
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