The basics of DNA testing for Family History Research

By Kitty Munson Cooper
Blogging at blog.kittycooper.com

My slides are always available at https://slides.com/kittycooper

Why Do A DNA Test?

  • Am I who I think I am?
  • Where were my ancestors from?
  • To find distant cousins who know more
  • To find an elusive ancestor

What DNA is Tested?

The test that most companies offer is for your autosomal DNA, your 23 pairs of chromosomes 

Three types of DNA tests

An autosomal DNA test looks at the DNA inherited

from ALL your ancestors

Your autosomal DNA test results in about 700,000 lines of data

Your genome contains about 3.1 billion base pairs from each parent 

only 700K of which are tested!

98% shared
DNA with him
99.9% with me

 

How can such a subset be useful?

 

The companies test the places that most often differ between people, known as SNPs

SNP - Single Nucleotide Polymorphism

a DNA mutation where a single letter chang3s

 

The tested SNPs were originally chosen for the ones with health implications and for those that could differentiate European ancestries. The companies keep updating the set they use

 

Can these SNPs really predict where your ancestors were from? 

NOT on a country basis for the most part

 only by Continent, usually several areas, North, South, East, West ....

  • West German looks French
  • East German looks Eastern European
  • South German can look Italian or East European
  • North German can look Scandinavian or English

Two European BioAncestries are clear in the DNA:

Ashkenazi Jewish

Finnish

But the others can overlap greatly

even more than shown in the map

for example German and English

BioAncestry  

usually cannot be determined on a country basis

map source: MyHeritage

Remember Kyle in the Ancestry DNA Adwho discovered he was Scottish not German?

Frankly it is hard to tell them apart as both can look Scandinavian or English...

It turned out his parents had used a Jewish sperm donor

Stan knew he was of 100% German descent!

These were his results at Ancestry

Be prepared for surprises from DNA Testing

Bill was one of the leaders of the Griffeth family History project but by testing his DNA he found that he was not a Griffeth

Can those 700K tested SNPs really predict your relationships? Yes for close relationships! But ...

Many relationships have overlapping ranges

https://dnapainter.com/tools/sharedcmv4

Simplified version of the relationship chart from the ISOGG wiki (courtesy Dimario, Wikimedia Commons)

... it is very difficult to tell the difference between a half sibling and a nibling (an aunt/uncle/niece/nephew) relationship from the amount of matching DNA.

Inheritance from 8 g-grandparents, courtesy of Angie Bush

You will not match all your 4th cousins or even all your 3rds

 

but you will match all your 2nd cousins

and closer relatives

What percentage of your cousins will match your DNA?

DNA testing can solve family puzzles ...

 

by finding cousins with more information

My grandmother Anna Lee

My great-grandma Maren Wold, my brick wall

I looked in every churchbook in Drammen for her with no luck!

He had photos of Maren's parents Jorgen and Anna Wold

Then I heard from a possible 3rd cousin who said, " I think your great grandmother is the sister of my great great grandfather."

Maren was actually from Skoger,now a suburb of Drammen

Part of Skoger is in Vestfold county not the same county as Drammen (Buskerud)

Records from the churchbook for Skoger in Vestfold

ThruLines at Ancestry shows a nice chart of the relationship if you and your cousin both have family trees there linked to DNA tests

Do I really have to look through thousands of matches?

Handling all those cousin matches

NO!

Start with the low hanging fruit, "extended family" about 3rd cousins or closer

(75cM and larger)

Cousin Matches

  1. How much shared DNA in centimorgans (cM)?
  2. Who else do they match? (Are they in your tree?)
  3. How many segments? (More than 2 is best)
  4. Closer cousins will have larger longest segments (20 cM or more especially if endogamous)

When you contact a possible cousin give them as much information as you can. Offer them photos and stories ...

Getting New Cousins to Respond to You

  • Have a family tree online
  • Upload friendly picture of yourself
  • Include details of who matches whom (they may have multiple kits)
  • Offer them information when you write to them

Do not be disheartened by lack of responses, some rarely log in 

Three types of personal DNA tests

Y test for father's father's line

mtDNA for mother's mother's line

Autosomal DNA test for all your ancestors

SNP - Single Nucleotide Polymorphism

a DNA mutation where a single letter chang3s

STRs are short tandem repeats

An extra copy is made of a sequence of DNA

An extra copy is made of a sequence of DNA

An extra copy is made of a sequence of DNA

An extra copy is made of a sequence of DNA

An extra copy is made of a sequence of DNA

2 Types of Y DNA Tests

Deep ancestry - haplogroup

More recent ancestry - surname studies

Y Haplogroups

By Chakazul, via Wikimedia Commons [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)]

Y Haplogroups

By Chakazul, via Wikimedia Commons [GFDL (http://www.gnu.org/copyleft/fdl.html)

Mitochondria under the microscope

Image Source: Dartmouth EM images, http://remf.dartmouth.edu/imagesindex.html
By User:Maulucioni via Wikimedia Commons [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)]

Mitochondrial Haplogroups

By User:Maulucioni via Wikimedia Commons [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)]

Mitochondrial Haplogroups

Why Do A DNA Test?

  • Am I who I think I am?
  • Where were my ancestors from?
  • To find distant cousins who know more
  • To find an elusive ancestor, solve a mystery

Where to test? It depends ...

 

  • 23andme.com*
  • Ancestry.com*
  • MyHeritage

The Big Three:

 

  • FamilyTreeDNA.com
  • LivingDNA

 

  • health results, chromosome browsers
  • biggest database, tree matching
  • more Europeans, trees and records
  • keeps sample, Y and mtDNA, chromosome browsers
  • has granular admix results for the British Isles

* These companies do not take uploads of tests from elsewhere

DNA Testing Basics for Genealogists

By Kitty Cooper

DNA Testing Basics for Genealogists

How personal genome tests can help a genealogist

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