DNA Testing
February 16, 2018
What Is DNA?
• Double helix – “ladder” structure where the rungs are
molecules called “nucleotides” or bases. DNA contains
only four of these nucleotides – A, G, C, T
• The sequence that these nucleotides occurs will determine
what protein is made. These proteins then will contribute
to “you” – all of your genetic and “phenotypic”
characteristics
• By reading the sequence of these nucleotides and
comparing to sequences commonly found in geographic
areas, your ethnicity can be predicted
Human DNA
• The entire DNA or
genome within a human
contains about 6 billion
nucleotides
• 99% are identical in all
humans; the 1%
difference results in
individuals
The Science Behind DNA Testing
• The DNA is isolated from
your sample (saliva, cheek
cells, etc.) and millions of
copies are made, using a
method called 'polymerase
chain reaction', or PCR.
• PCR uses a naturally
occurring enzyme to copy
a specific stretch of DNA
over and over again.
Testing DNA “Snippets”
Why Send in Your DNA for Testing?
• Ancestry will send you a pie chart with your
predicted ethnicity percentages
• Ancestry will continually search for relatives
based on shared DNA and send you email
alerts
• But – don’t trade in your lederhosen yet for a
kilt – your ethnicity % are estimates
• Each company uses different databases and
“best guesses” as to your background (more
info to follow)
Which Company Should You Choose?
Company Features
42+ ethnic regions, some of which are exclusive to MyHeritage
More focused ethnicity specifics than other main-market solutions
Great experiential results including animations and soundtrack
Easy integration with other MyHeritage features (some of which require additional payment)
8 billion historical documents, 300 million photographs, 34 million family trees. 2.1 billion names
Autosomal DNA testing
“Shared Ancestor Hints” find intriguing connections for you
Specific results: 150 ethnic regions, 5 times more than the next leading DNA test
Connect with 90,000,000 family trees and billions of historical records
DNA samples are stored forever, so you never have to re-test
Create “DNA Circles” of probable relatives
Highly-detailed results broken down to regions within countries
Tracing ethnic heritage back 10 generations
Y, mt and autosomal testing
Interactive map to follow your ancestors migrations
Highly-advanced testing that implements the know-how of over 100 expert scientists
Provides raw data results which can be used on other genealogy sites
Inheritance tracing
Ancestry percentages to the 0.1%:
Chromosome breakdown of ancestry: See which pieces of your DNA come from 31 populations
worldwide
Compare DNA Relatives' segments
Opt-in health and ancestry option
• 23andMe reference datasets include genomes from 10,418
people who were carefully chosen to reflect populations
that existed before transcontinental travel and migration
were common (at least 500 years ago).
• Most of the reference individuals are 23andMe customers
who have consented to participate in research. When a
23andMe research participant tells us that they have four
grandparents all born in the same country — and the
country isn't a colonial nation like the US, Canada, or
Australia — that person becomes a candidate for inclusion
in the reference data.
23andMe Unique Features
Ancestry.com
• Largest and most diverse database compared to other
testing kits: connect with 90,000,000 family trees and
billions of historical records
• Over 6 million users
• Offers information both on the distant past, as well as
more recent relatives and your family tree
• Pricing is one of the lowest on the market ($79)
• Will search for matches for you and email the
connections to you
• One con: does not provide health information
Ancestry DNA Testing
• Ancestry uses microarray-based autosomal DNA testing
that surveys the entire genome at over 700,000 sites
• Autosomal DNA simply means the DNA found in a
chromosome inherited from both your father and mother,
and contains bits of genetic sequences from past
generations.
• Close relatives share large fragments from a common
ancestor, while the matched fragments get smaller from
more distant ancestors
What Kinds of DNA Tests Do Genealogy
Companies Use?
• The Y chromosome test allows you to follow only the paternal line.
Males carry one Y chromosome that determines gender. If XX, then the
child is female; is XY, the child is male. The Y test follows the inherited
Y chromosome sequences. This test can go back as far as 25 generations.
• The mitochondrial (mt) DNA test follows the maternal line. Only
females pass on the small amount of DNA found in the mitochondria of
cells. This test also goes back 25 generations.
• The autosomal DNA test looks at locations on all chromosomes that
companies have decided are best “ethnic” matches. Therefore, this test
follows both maternal and paternal. But, this test can only go back as far
as 5-6 generations.
Autosomal DNA Testing
• The chance that an autosomal DNA test will accurately detect a
relative decreases with the distance of the relationship. For
example, most autosomal DNA ancestry tests predict an
accuracy rate of 90–98% when detecting a match with a 3rd
cousin, but around a 45–50% chance of detecting a match with a
fourth cousin.
• The amount of autosomal DNA shared with a relative decreases
with each successive generation.
• 50% - parents and siblings
• 25% - grandparents, half-siblings, aunts/uncles, double first cousins
• 12.5% - first cousins
• 6.25% - first cousins, once removed
• 3.125% - second cousins, first cousins twice removed
Confidence Levels in Ancestry
• The confidence score for your DNA matches is based on the
amount and location of the DNA that you share with that
potential match. A high confidence score means that its almost
certain that the DNA sequence you share with a match is
identical because it was inherited from a recent common
ancestor.
• The confidence score is related not to whether you are 4th cousins
or not, but that you are related through a common ancestor
(discuss more on the website demonstration).
• The chance of a match decreases with each successive generation
• 90-98% when detecting a match with a third cousin
• 45-50% with a fourth cousin
Ancestry DNA Results
DNA Test of Siblings
17% Germany 29% Germany
23% Scandinavia 21% Scandinavia
9% Ireland/Scotland/Wales 14% Ireland/Scotland/Wales
Mother-Daughter Results
Mother –Son Results
British/Irish
4%
2% Scandinavian
25% French/German
47% Finnish
1% NW European
6%
15% S European
Broadly European
Using the Shared DNA Tool in Ancestry
• The Shared Matches tool will show which matches you and any
given match on your list share in common. You can use this
new tool to help narrow down your matches to a particular side
of your family. It’s especially helpful if you’ve had a parent
tested because once you have a parent tested, you’ll see a new
filter at the top of your match list that lets you find the DNA
matches that you share with your mom or dad.
• I have had a 1st cousin tested, and I can now see all the matches
we share. From this list I can possibly narrow down to those
matches that might stem from a common ancestor, and not have
to search through all the matches.
Using the Shared Tool
DNA Testing Limitations
• DNA tests analyze less than 1 percent of a person's genome; they
will miss most of a person's relatives.
• DNA snippets, or markers, are inconsistent. Sometimes they are
passed on and sometimes they are not, and whether they are or
aren’t is random.
• When a DNA test comes back saying you are 28% Finnish, all it’s
really saying is that of the DNA analyzed, 28% of it was most
similar to that of a completely Finnish person (and what does
“completely Finnish mean?).
• People are continuously moving and reproducing with other,
diverse people. If anything our DNA is getting more muddled, not
more clear.
Examining the Ancestry DNA site in detail
