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Forum: Family Finder Basics 13th January 2018, 06:41 PM
Replies: 6
Views: 837
Posted By John McCoy
The "ethnicities" that are measured are actually...

The "ethnicities" that are measured are actually statistical constructs based on DNA samples from contemporary (living) humans who claim to have ancestry in various places. There are many...
Forum: DNA and Genealogy for Beginners 11th January 2018, 01:42 PM
Replies: 1
Views: 99
Posted By John McCoy
The matching segments are likely too small to be...

The matching segments are likely too small to be of any genealogical use, even though they may be "real".

X matches are often difficult to interpret. The ones that are probably worth the trouble...
Forum: BIG Y and SNP Discovery 8th January 2018, 10:45 AM
Replies: 23
Views: 1,182
Posted By John McCoy
You might have a different take on the matter if...

You might have a different take on the matter if you were named Buchanan! A large number of Buchanans have taken the Big Y test, and it is now clear that they fall into distinct groups defined by...
Forum: Y-DNA Haplogroups & SNPs Basics 7th January 2018, 11:43 AM
Replies: 4
Views: 185
Posted By John McCoy
Autosomal testing (such as Family Finder) is very...

Autosomal testing (such as Family Finder) is very good at detecting close relationships, out to about third cousins (although the rule of thumb is that about 10 percent of actual third cousins...
Forum: X-DNA Basics 3rd January 2018, 06:44 PM
Replies: 8
Views: 232
Posted By John McCoy
So the PAR regions are indeed quite short in...

So the PAR regions are indeed quite short in terms of the human genetic recombination map -- short enough that I don't think they are likely to be significant sources of error in interpreting strong...
Forum: X-DNA Basics 3rd January 2018, 01:14 PM
Replies: 8
Views: 232
Posted By John McCoy
Does anyone have the lengths of the 2 PAR regions...

Does anyone have the lengths of the 2 PAR regions on the X chromosome in centiMorgans?
Forum: X-DNA Basics 3rd January 2018, 10:20 AM
Replies: 8
Views: 232
Posted By John McCoy
First consideration for an "X match" is its size....

First consideration for an "X match" is its size. If the matching segment is small (say, 10 cM or less), it's unlikely to be genealogically useful in any way, based on the collective experience of a...
Forum: Family Finder Basics 2nd January 2018, 05:55 PM
Replies: 28
Views: 1,061
Posted By John McCoy
In my experience, the "estimated generations to...

In my experience, the "estimated generations to the Most Recent Common Ancestor" on GEDmatch, and perhaps also about the same for FTDNA and Ancestry estimated relationships, is reasonably aqccurate...
Forum: Y-DNA Haplogroups & SNPs Basics 30th December 2017, 07:34 PM
Replies: 1
Views: 209
Posted By John McCoy
I tend to agree with your caution on Y-111. It...

I tend to agree with your caution on Y-111. It produced no particularly useful information for me -- there were one or two matches, but just not close enough to suggest any new research strategy. ...
Forum: DNA and Genealogy for Beginners 28th December 2017, 11:04 AM
Replies: 10
Views: 497
Posted By John McCoy
Thank you Ann! A very interesting finding,...

Thank you Ann!

A very interesting finding, that imputation can end up comparing more SNP positions, but at the same time result in enough additional mismatches to interfere with the matching...
Forum: BIG Y and SNP Discovery 26th December 2017, 05:31 PM
Replies: 23
Views: 1,182
Posted By John McCoy
Also, at this stage, there is apparently a...

Also, at this stage, there is apparently a residuum of Big Y kits that haven't been "reprocessed" yet. Consequently, the lack of matches for some kits could simply be the result of incomplete...
Forum: DNA and Genealogy for Beginners 26th December 2017, 11:54 AM
Replies: 10
Views: 497
Posted By John McCoy
It's a big IF, as you can imagine! For...

It's a big IF, as you can imagine!

For imputation to work properly, without introducing false matches, it seems necessary to demonstrate first that SNP A is associated with a very closely-linked...
Forum: DNA and Genealogy for Beginners 18th December 2017, 10:49 AM
Replies: 2
Views: 248
Posted By John McCoy
The number of no-calls has nothing to do with how...

The number of no-calls has nothing to do with how you uploaded your DNA data file. Uploading it again will produce the same result. It would be interesting to know if FTDNA thinks your Family...
Forum: Features Requests & Bug Reports Area 13th December 2017, 10:47 AM
Replies: 8
Views: 413
Posted By John McCoy
While it is possible to build your family tree on...

While it is possible to build your family tree on the FTDNA web site, I strongly recommend that you maintain your personal research on a genealogy software program on your home computer, where you...
Forum: BIG Y and SNP Discovery 6th December 2017, 07:12 PM
Replies: 5
Views: 454
Posted By John McCoy
That raises a question. Are your Big Y results...

That raises a question. Are your Big Y results "final", and you are officially L20*? Or, are you just generic L20, and the rest of the data from your Big Y test hasn't been posted yet, that might...
Forum: Paternal Lineage (Y-DNA STR) Basics 5th December 2017, 10:11 AM
Replies: 3
Views: 550
Posted By John McCoy
The TiP report, of course, is only an estimate of...

The TiP report, of course, is only an estimate of the probabilities, based on a number of untested assumptions. Even if it happened to yield a close approximation of the actual distribution of...
Forum: Family Finder Basics 4th December 2017, 05:00 PM
Replies: 2
Views: 223
Posted By John McCoy
Possible, but using X matches alone, without a...

Possible, but using X matches alone, without a strong autosomal match, seems to be difficult. And you have to be sure the X segments are long enough to be "significant" -- which I expect means at...
Forum: Paternal Lineage (Y-DNA STR) Basics 1st December 2017, 06:06 PM
Replies: 2
Views: 231
Posted By John McCoy
There might possibly be an explanation if the...

There might possibly be an explanation if the estimated mutations rates for each STR were sufficiently different and in exactly the right direction, but it sounds unlikely to me too.
Forum: BIG Y and SNP Discovery 23rd November 2017, 06:33 PM
Replies: 153
Views: 12,770
Posted By John McCoy
I'm guessing the main update process has...

I'm guessing the main update process has completed, and there is now a residual group of kits that ran into issues and that have to be reviewed individually. That's not necessarily a bad thing. ...
Forum: BIG Y and SNP Discovery 23rd November 2017, 10:54 AM
Replies: 10
Views: 559
Posted By John McCoy
It might be useful to remember that even when we...

It might be useful to remember that even when we have ancient DNA samples to work with, they only place an upper bound on the "birth dates" of SNP's. For any SNP, the earliest date we find only...
Forum: BIG Y and SNP Discovery 21st November 2017, 11:01 AM
Replies: 10
Views: 559
Posted By John McCoy
The key question here, I think, is the range of...

The key question here, I think, is the range of variation of mutation rates and the accumulation of mutations observed in a population of Y chromosomes -- and I don't think there is enough data to...
Forum: Grumbles & Gripes 16th November 2017, 02:36 PM
Replies: 3
Views: 410
Posted By John McCoy
Testing a few known relatives (parents, cousins,...

Testing a few known relatives (parents, cousins, aunts & uncles), if you can convince them to participate, is an enormous help in identifying matches, since you can more easily work out which matches...
Forum: Family Finder Advanced Topics 15th November 2017, 10:43 AM
Replies: 8
Views: 445
Posted By John McCoy
When the Family Finder results come back, you can...

When the Family Finder results come back, you can upload both DNA files to the free GEDmatch web site. The GEDmatch "One-to-One" comparison tool has a "graphics option" that will display both the...
Forum: Family Finder Basics 1st November 2017, 10:19 AM
Replies: 1
Views: 347
Posted By John McCoy
If all of the kits you are triangulating match...

If all of the kits you are triangulating match each other over most of this segment, yes, it is definitely significant. However, the more difficult problem is often to work out who the common...
Forum: Paternal Lineage (Y-DNA STR) Basics 30th October 2017, 01:47 PM
Replies: 9
Views: 800
Posted By John McCoy
Most of the time, maybe 90 percent, third cousins...

Most of the time, maybe 90 percent, third cousins (descendants of a common great-great-grandfather) will be detectable as autosomal matches through the Family Finder test. Whether FTDNA actually...
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