Geneticists: tracing DNA to a specific individual

In 1998, DNA testing proved that Thomas Jefferson (of Declaration of Independence fame) fathered at least one of Sally Heming's sons. However, they were able to do this by having an unbroken male line from both Sally's son Eston and sons borne by Thomas's wife Martha. This allowed them to compare the Y-chromosome which is only passed down the male line (indeed, it's what makes males males). You can do something similar with mitochondrial DNA which is only passed from the mother.

That work in regard to Jefferson only showed that someone with the same Y chromosome as T.J. was the father of one of Sally Hemmings sons. There is evidence to indicate that it may have been one of Jefferson's cousins.

As to the original question, Y chromosomes can be traced, but that doesn't work with X chromosomes, but it does work with mitochondrial DNA, which is only inherited from the maternal line.

In either case it can be shown that someone had the same Y or mtDNA, but both are shared by great numbers of people. They would all be related are some degree, but getting more precise is always a matter of probabilities.

Using mitochondrial DNA, a schoolteacher in Cheddar England was determined to be a very close relative of Cheddar Man, who lived 9000 years ago. (Descent through the female line, obviously.) And apparently a couple of kids in his class were too.

benbenberi said:

Using mitochondrial DNA, a schoolteacher in Cheddar England was determined to be a very close relative of Cheddar Man, who lived 9000 years ago. (Descent through the female line, obviously.) And apparently a couple of kids in his class were too.

Click to expand...

It just shows you that some people never move.

A lot has been done on checking on who was related to whom with Egyptian pharaoh Dynasties and there was also last year, showing that the bones under the car park were Richard III - checked the bones DNA and those of a man known to be a family descendent. You could do searches for articles on those and look at the details.

Amazed by the Cheddar story - though not surprised if that makes any sense. Nice to know.

Also beats "came over with the Mayflower" into a cocked hat.