Genetic Genealogy

Irish Family History: Intermediate level

6 p.m. Tuesday 12 November 2019 and Tuesday 19 November 2019

Room 5052, Arts Building, TCD

by Paddy Waldron

WWW version:

http://pwaldron.info/TCD/intermediate

YouTube version:

12 November - not recorded due to Camtasia failure; 19 November - https://www.youtube.com/watch?v=4onBrYrPdZE

***** NB: FamilyTreeDNA kits will be available after this talk for anyone interested via the DNA Outreach IRL project *****

Outline

Review of beginners' session

male offspring female offspring
sperm Y chromosome X chromosome
22 paternal autosomal chromosomes
egg X chromosome
22 maternal autosomal chromosomes
mitochondria
DNA component Inheritance path Inherited by
Y chromosome From father only (and only if male) males only
autosomal chromosomes (autosomes) Equally from both parents everyone
X chromosome(s) Unequally from both parents males x1, females x2
mitochondrial DNA From mother only everyone

Identity v. Anonymity

The basic rules for successful use of the DNA websites include the following:
Reveal the DNA subject's birth surname:
Most people inherit DNA with their birth surname, so identify yourself as a minimum by your birth surname with an initial or a title, e.g., P Waldron or Mr Waldron or Miss Durkan.
Reveal the gender of the person who provided the DNA sample:
A woman does not have a Y chromosome, so may ask a male relative with the relevant surname to swab:
    a father, brother, nephew, cousin, etc., if her interest is in her maiden surname; or
    a husband, son, brother-in-law, father-in-law, etc., if her interest is in her married surname.
Valuable additional inferences can potentially be drawn once it is known whether two X chromosomes (female) or one X chromosome and one Y chromosome (male) are potentially available for comparison.
You must NOT attach a female name to a male DNA sample (or vice versa), as this causes untold confusion.
Be especially careful not to inadvertently link a male's Y-DNA results with a female's autosomal DNA upload at FamilyTreeDNA.com where error-checking does not look for this.
Also take care not to link a male DNA sample to a female's pedigree chart (or vice versa).
Avoid providing irrelevant information:
Your first name, married surname, adopted surname or marital status reveal nothing about your DNA, so you may keep these private if you wish.
Avoid pseudonyms:
They reduce the chances that your matches will bother to look at your family tree, contact you or share the information about your ancestry that they have and that you do not have.
Use a photograph:
If you upload a photograph to your AncestryDNA account before you receive your initial results, then the photograph (hyperlinked to the match details) will appear on the AncestryDNA Insights page of all your matches as long as you remain in their eight newest matches with photographs.
Be consistent and avoid unnecessary confusion:
A real example (further anonymised):
Keep all your DNA-related correspondence in a single searchable e-mail archive
Use the internal messaging system and AncestryDNA/MyHeritage/23andMe or Facebook messages only to exchange e-mail addresses.

Fishing in all the gene pools

There are a growing number of DNA comparison websites and those interested in finding long-lost relatives should be in all of them. While helping an adoptee who is married to a Murphy, I coined what I have called Murphy's Law of Genetic Genealogy:

If there are N DNA comparison websites and your DNA is in N-1 of them, then your most important match will be in the Nth.

In the words of another widely used metaphor, there are many online gene pools out there and there are many people who are in only one or two of them; for maximum effect, particularly if you are trying to find an unknown ancestor who has left no paper trail, you must fish in all of these pools.

You must spit for the websites which do not allow data uploads:

You must download your data file from the website of whichever laboratory you use and upload it to the websites which do allow data uploads:
You must link your DNA match list and your pedigree chart and share them on the major autosomal DNA comparison websites:
Add DNA information to your genealogy database:
Add genealogy information to the online DNA databases:

GEDmatch.com tools

These tools are free to all users:

If you login in one browser tab, then you can open these Tier 1 tools (USD10/month) in another tab:

FamilyTreeDNA.com tools

AncestryDNA tools

MyHeritage.com tools

Other third party tools and websites

Using autosomal DNA shared matches, triangulation and phasing

Shared, or In Common With (ICW), matches

A group of three or more individuals who all meet the relevant matching criteria with each other are likely to share a recent common ancestor (or, more often, ancestral couple).

When I find a new match, I am usually anxious to identify the most distant known ancestor through whom I am related to the new match.

The matches that I share with the new match are usually the first clue to solving this puzzle.

All of the DNA comparison websites allow one to identify the shared matches of two individuals in some form or another.

The matching criteria vary from one DNA comparison website to another.

The stricter the matching criteria, the more significant the shared matches.

FTDNA Family Finder

To find the shared matches of two individuals who match each other:

You will eventually identify a group of individuals, all of whom you suspect descend from a single common ancestor (or ancestral couple).

To see whether up to 10 individuals who match you also match each other:

To find the shared matches and shared cM of two or more individuals who belong to the same project, whether or not they match each other:

AncestryDNA

On each match page, there is a Shared Matches link. (Screenshot.)

The Shared Matches are those with Shared DNA of 20 cM or more with both individuals.

So C can appear in the shared matches of A and B even if B does not appear in the shared matches of A and C (if C shares more than 20cM with A but B shares less than 20cM with A).

Matches are sorted by closeness of relationship to the logged-in individual.

A can see that B matches C but cannot see the cM shared by B and C.

MyHeritage

When the Review DNA Match page eventually completes loading, the Shared DNA Matches section:

Matches are sorted by the sum of the centiMorgans shared with the two individuals.

A can see not only that B matches C but also the cM shared by B and C.

A's shared matches with B will be exactly the same as B's shared matches with A, in the same order.

GEDmatch

To find the shared matches of two individuals, whether or not they match each other, use the "People who match both, or 1 of 2 kits" tool on the many menu.

This lists shared matches of Kit 1 and Kit 2, no matter how much DNA or how little DNA Kit 1 shares with Kit 2.

Matches are sorted by closeness of relationship to Kit 1.

To sort by closeness of relationship to Kit 2, re-use the tool with the kits in reverse order.

If you login in one browser tab, and open the Multi Kit Analysis menu in another tab (via a hyperlink or bookmark), then you can run an Autosomal Matrix Comparison on up to 100 kits.

While the FTDNA user matrix shows only whether or not kits match, the FTDNA administrator matrix and the GEDmatch matrix shows the shared centiMorgans.

Triangulated matches

Triangulation and phasing are really opposite sides of the same coin.  If V is half-identical on the same region with W and Z, then there are two possibilities:

  1. W and Z are half-identical to each other on this region, in which case V, W and Z probably inherited an identical segment in this region from a single common ancestor and the relationship can be described as triangulated; or
  2. W and Z are not half-identical to each other on this region, in which case V is probably related to W on V's paternal side and V is probably related to Z on V's maternal side, or vice versa, and V's autosomal DNA in this region can be phased.

The ADSA tool by Don Worth at DNAGedcom provides a graphical representation of triangulation and phasing.

Triangulation groups

The ultimate objective is to collect DNA matches into triangulation groups. A triangulation group is a set of three or more people who are all half-identical to each of the other group members on overlapping regions.

The more individuals who are added to the triangulation group, the smaller the overlap may become.

A triangulation group of three or more individuals are very likely to share a recent common ancestor (or, more often, ancestral couple).

he triangulated matches that I share with a new match are usually the second clue to identifying through which of my most distant known ancestors I am related to the new match. Some of the DNA comparison websites allow one to identify the triangulated matches of two individuals in some form or another.

FTDNA Family Finder

One had to be a little devious to find triangulated matches directly at FTDNA. The methodology may change when the current website changes are completed:
Your family tree is currently updating to a new version. • Your DNA Matches may be missing their family tree links because their family tree has not yet been updated to the new version. Once a match’s family tree is successfully updated, this function will become available. All customer trees should be updated to the new version by November 30th.
The Linked Relationship feature was designed to identify matches who triangulate with known third cousins or closer, and then dump them all together again in paternal and maternal buckets.

If the new family tree system is similar to the old, then you may want to have two Family Finder kits, e.g. a kit based on swabs sent to FTDNA with a full pedigree chart for paternal/maternal phasing; and a kit based on an autosomal transfer from another laboratory with a minimal pedigree chart for identifying triangulated matches (e.g. my B95575).

AncestryDNA

AncestryDNA refuses to provide any way of identifying triangulated matches.

MyHeritage

MyHeritage shared match lists include a symbol identifying which of these matches are triangulated.

There appears to be no way to filter the list of shared matches to show only the triangulated matches.

GEDmatch

To use the triangulation tools, you are expected to subscribe to Tier 1 (USD10 for one month).

If you login in one browser tab, then you can open these Tier 1 tools in another tab:

Y-DNA and surname projects

Further reading