The O'Dea/O'Day/Dee DNA Project

10th International O Dea "Clan" Gathering 2018

10:30 a.m. Friday 11 May 2018

Banner Room, Old Ground Hotel

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.

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 O'Dea/O'Day/Dee DNA Project.

You 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.

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

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 the project, rather than waste money merely confirming known relationships.

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

Overlaying SNPs and Surnames

The Irish annals tell us that Cas was the "father" of the O'Deas, O'Briens, O'Quinns, MacNamaras and other surnames - the Dalcassian surnames.

Deaghaidh, from whom the surname is derived, lived 12 generations before Conor, victorious in battle 700 years ago this week, so it is not strictly correct to claim Conor as "our great ancestor".

Genetic similarities are being found between men with these related Dalcassian surnames.

They generally have Irish Type III DNA characterised by the L226 SNP in Haplogroup R.

There is a project set up at Family Tree DNA for the R-L226 Haplogroup.

Many thanks to Dennis Wright, Dennis O'Brien and Robert Casey who administer that project for all their advice on interpreting O'Dea Y-DNA results.

Surname-specific SNPs are now being discovered and will eventually be discovered for the O'Dea surname.

The O'Dea/O'Day/Dee DNA Project

The Y-DNA Results

The results reveal various different independent genetic origins of the O Dea surname, both inside and outside the Dalcassian branch of the haplotree.

The O'Dea/O'Day/Dee Surname Project now has 52 members with STR results visible to project members and administrators, of whom 27 have made their STR results visible to the public.  So remember to log in to your FTDNA account if you want to see the full results table; and to adjust your privacy settings if you want others to see you in the full results table..

Surname spelling distribution:
I have provisionally divided these members into 18 O'Dea subgroups, based mainly on their STR results, with a residual group for those whose O'Dea ancestry which is not through the patrilineal line.

So far, sixteen of the men whose surname is O'Dea or a variant have given a placename in the Paternal Ancestor Name column, eleven in Ireland (Counties Clare, Cork, Galway and Limerick and one from an unspecified county), two (known relatives) in Wales, one in Canada and one in the USA.

The confirmed terminal SNPs for men in the O'Dea subgroups to date are:
(Heat maps from Wikimedia Commons.)

The Dalcassian O'Deas: Breaking News

FGC5660, DC135, DC134 and BY5212 are descendants of the better-known R-L226 (Irish Type III or Dalcassian Y-DNA signature), which accounts for over half of the O'Dea men in the project (27 out of 52).
Almost all L226+ men are also FGC5660+.
The O'Dea with terminal SNP L226 has bought only the single SNP L226 test, so is probably also FGC5660+.
John B O'Day III was the first Dalcassian O'Day or O'Dea to buy BigY:
Commentary by Dennis O'Brien and Robert Casey of the L226 project:
"Where has this member come from?
If he is BY5212+ then he should certainly be in the O’Brien Surname Project like Morrissey.
As YFS231286 is certainly a “Thomond” SNP of around 1300AD, this person has to be either a NPE, adoption or political surname change.
What do we know about his history?
Except for Morrissey, this has not happened, to our knowledge, before."

"This puts you at a descendant of King Brian Boru.
I highly recommend that you upgrade this person to either 67 markers or 111 markers.
The L226 O'Dea testers belong to at least five different branches (both confirmed and predicted) under L226 that would not share a common ancestor with the O'Dea surname [see L226 results page]:

Group 11: FGC5660/Z17669-    4    67 markers (Kilteely group)
DC41           1    67 markers (kit 84924? Not in O'Dea project?)
DC63           1    67 markers (kit 517547)
Group 74a: BY5212       1    37 markers (John B O'Day III)
Group 12a: DC135         1    37 markers (James O Dea)

Then there are five more O'Dea testers at 37 markers that could predicted at 67 markers."
Within the L226+ subgroup, one O'Dea has tested positive for DC135 (and hence must be DC8+ according to the FTDNA haplotree) but another is DC8- and two are DC8*.  This raises the question as to whether the DC8 mutation or the adoption of the O'Dea surname by this group of O'Deas came first.  So far, there are only four men in this branch of The Big Tree and none of them is an O'Dea (or variant). There are several Crow/Crowe/Croke men on the DC135 branch which suggests a close connection between those surnames and O'Dea. One of the Crokes has joined the O'Dea project.

So far, there are only seven Big Y500 (formerly known as BigY) results in the project, with most recent confirmed SNPs:
One objective of the project is to identify one or more O'Dea-specific SNPs within the R-L226 subgroup. This will require more O'Deas (or variants) from that subgroup to purchase Big Y500. With any luck, another man with Big Y500 results will eventually share one of the novel variants of an existing Big Y500 subject, which will then be deemed to be a new SNP.

My own O'Dea Ancestry

The Future