The Clans of County Clare: Combining archives, annals and Y-DNA

Clans and Surnames: Irish Family Research

3:00 p.m. Thursday 17 May 2018

Abbeycourt Suite, Great National Abbeycourt Hotel, Nenagh, Co. Tipperary

by Paddy Waldron

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Where does our Human DNA come from?

male offspring female offspring
sperm Y chromosome X chromosome
22 paternal autosomes
egg X chromosome
22 maternal autosomes

Inheritance Paths

Y chromosome
Only males have a Y chromosome.
The Y chromosome comes down the patrilineal line - from father, father's father, father's father's father, etc.
This is the same inheritance path as followed by surnames, grants of arms, peerages, etc.
X chromosome
Males have one X chromosome, females have two.
X DNA may come through any ancestral line that does not contain two consecutive males.
Blaine Bettinger's nice colour-coded blank fan-style pedigree charts show the ancestors from whom men and women can potentially inherit X-DNA.
Exactly 50% of autosomal DNA comes from the father and exactly 50% comes from the mother.
Due to recombination, on average 25% comes from each grandparent, on average 12.5% comes from each greatgrandparent, and so on.
Siblings each inherit 50% of their parents' autosomal DNA, but not the same 50% (except for identical twins).
Everyone has mitochondrial DNA.
Mitochondrial DNA comes down the matrilineal line - from mother, mother's mother, mother's mother's mother, etc.
The surname typically changes with every generation in this line.
As this is a Clans and Surnames event, this talk will concentrate on Y DNA, which is associated with surnames.

Mutations: STRs, SNPs and Haplogroups

Most DNA is transcribed exactly from the relevant parent to the child.

Mutations are transcription errors at single locations, e.g. a single A in the parent may be replaced by a C in the child.

Some locations mutate very frequently (every couple of generations), and can be used to identify individuals beyond reasonable doubt, e.g. in criminal cases.

Some locations mutate less frequently (only once in many generations or once in the history of mankind), and can be used to identify closely or distantly related individuals.

Special types of mutations:
FamilyTreeDNA will (for a fee) examine your Y chromosome (if you have one) for both STR and SNP mutations.

STR mutations can reverse or repeat in later generations, but some SNP mutations on the Y chromosome are once-in-the-history-of-mankind events. These mutations have occurred exactly once. Every man descended from the man in whom the mutation originally occurred inherits the mutation. No other man has the mutation. When discovered, each of these SNPs is given a label consisting of letters followed by numbers, occasionally including an underscore (_), e.g. L226 or FGC5660 or ZZ33_1.

Men with a more recent SNP may share older SNPs with men who don't have the recent one.

Note that surname spellings also mutate, independently of DNA mutations, e.g. ” Deaghaidh to O'Dea to O'Day.

The Pros and Cons of Public DNA Comparison

Submitting DNA Samples

The entry-level Y-DNA product is now Y-DNA37, which looks at the numbers of repeats for each of 37 STR markers on the Y chromosome, e.g. the Clare Roots Project.

FTDNA customers may want to turn off usually irrelevant Y-12 and Y-25 match notification e-mails on the Notification Preferences page.

In return for your DNA sample, you will get:
The word haplogroup has long been used to describe any group of men with similar Y-DNA (or a group of people with similar mtDNA):
SNPs can be used to build a Y-DNA Haplogroup Tree or haplotree, with more recent SNPs shown as children of  older SNPs.

There has been a SNP Tsunami in recent years: from about 800 SNPs in 2012 to more than 35,000 SNPs by 2015.

Some branches of the haplotree:
The Y chromosome is only 59,373,566 letters long, so there is an upper bound to the number of SNPs that may eventually be discovered.

Men with the same SNP mutation tend to also have similar patterns of STR mutations, so STR mutations are used to predict SNP mutations.

FTDNA now uses "haplogroup" (on the Y-DNA Colorized Chart) interchangeably with  "Terminal SNP" (on the Y-DNA - Matches page).
STRs can only predict Y haplogroups but a SNP product must then be purchased to confirm the Y haplogroup:
Known relatives should pool their funds to purchase more advanced testing or donate to relevant projects, rather than waste money merely confirming known relationships.

Donations to FTDNA projects must be used to purchase FTDNA products for members and can not be used for any other purpose.

Overlaying SNPs and Surnames

Sometimes the Irish annals tell us that certain groups of surnames can be expected to have similar Y-DNA signatures.

Sometimes Y-DNA results tell us that certain groups of surnames are closely related.

Sometimes Y-DNA results tell us that common surnames have multiple independent origins.

Example 1: The Dalcassian surnames

Example 2: The Corcomroe (Corca Modhruadh) surnames

Example 3: Specific surname projects

The more common a surname, the more independent genetic origins it appears to have:

The Future