For Genetic Genealogy, which is the application of DNA testing to genealogy research,
two areas of DNA have shown to provide information that can be used in conjunction
with genealogy research. These two areas are the Y chromosome and mtDNA. These areas
of the Y chromosome and mtDNA do not contain information about a persons traits
or medical information. For example, the Y DNA area is known as Junk DNA by the
scientists, since it does not code for personal information.
An individual's test results have little meaning on their own. You cannot take these
numbers, plug them into some formula and find out who your ancestors are. The value
of the test results depends on how your results compare to other test results. And
even when you match someone else, it will only indicate that you and the person
you match share a common ancestor. Depending on the number of markers tested and
the number of matches it will indicate with a certain degree of probability how
long ago this common ancestor existed. It will not show exactly who this ancestor
is. That must be investigated through traditional genealogical research.
The Y-Chromosome is passed from father to son. The vast majority of the time the
father passes an exact copy of his Y-Chromosome to his son. This means that the
markers of the son are identical to those of his father. However on rare occasion
there is a mutation or change in one of the markers. The change is either an insertion
or a deletion. An insertion is when an additional repeat is added to a marker. A
deletion is when one of the repeats is deleted.
Mutations occur at random. This means it is possible for two distant cousins to
match exactly on all markers while two brothers might not match exactly. Because
of the random nature of mutations we must use statistics and probability to estimate
the Time to the Most Recent Common Ancestor (TMRCA). The actual calculations of
TMRCA are mathematically complex and depend on knowing the rate of mutation and
the true number of mutations.
What About DNA Testing?
by US312 Wayne Straight
A while ago, I authored a number of e-mails on Yahoo's Ontariogenealogy list
in response to queries about DNA. Marie Spearman has since asked me to do a reprise
of that exchange. After looking at it, and at subsequent e-mails from much more
knowledgeable people, I decided to try to synthesize what I had to say with the
> A brief background on genetics
Spread of H. Sapiens Worldwide
US332 Wayne Straight shared a fun link (http://www.bradshawfoundation.com/journey/). Its an animated view of the spread
of H. Sapiens across the world. It was developed by Stephen Oppenheimer who wrote
“The Origins of the British”, a study of the peopling of the British
Isles based on genetics, archaeology, and linguistics.
There is also a a 2-part video on Youtube in which Mr. Oppenheimer talks about his
findings in re British genetics. Unfortunately he's a better writer than speaker—a
problem shared by yours truly I must admit.
View Part 1
View Part 2
And finally, here’s a very succinct (2.5 minutes) summary of Oppenheimer’s book
and lecture. View
Oppenheimer British DNA Summary