Go Back   Family Tree DNA Forums > Paternal Lineages (Y-DNA) > Paternal Lineage (Y-DNA STR) Advanced

Paternal Lineage (Y-DNA STR) Advanced Users can exchange information here on Y-DNA testing, results, and questions.

Reply
 
Thread Tools Display Modes
  #1  
Old 8th July 2018, 06:43 PM
stev703 stev703 is offline
FTDNA Customer
 
Join Date: Jan 2015
Posts: 12
Question 2 mutations in 3 generations

Hi, I have 2 kits from men who are 2nd cousins. They share a common Great Grandfather. One of the cousins matches another known descendant of the same great grandfather at 0 GD at 111 markers. The other of the two cousins shows 2 GD at 111 markers. Evidently there were two mutations in the 2 GD line in 3 generations.
My questions would be first, what are the odds of this occurring, and second, what does this rapid? mutation mean to the Y's usefulness as a tracking method with this line?
Thanks for any input.
Reply With Quote
  #2  
Old 8th July 2018, 09:42 PM
prairielad prairielad is offline
FTDNA Customer
 
Join Date: Feb 2011
Location: Canada
Posts: 2,023
My father and his paternal 1st cousin are a GD of 4 at the 37 marker level. My father and his brother are a GD of 1 (my uncle to same cousin a GD of 3). All three as well as another match ( all share same 2x great grandfather) share an unique marker mutation which set us apart from all other surname matches. My father's cousins markers are the closest to all other of their surname matches

Mutations happen a anytime, thus it can be benificial to test multiple lines to aid in ruling out any recent mutations which can skew predictions
Reply With Quote
  #3  
Old 8th July 2018, 11:12 PM
georgian1950 georgian1950 is offline
FTDNA Customer
 
Join Date: Jun 2012
Posts: 749
Quote:
Originally Posted by stev703 View Post
Hi, I have 2 kits from men who are 2nd cousins. They share a common Great Grandfather. One of the cousins matches another known descendant of the same great grandfather at 0 GD at 111 markers. The other of the two cousins shows 2 GD at 111 markers. Evidently there were two mutations in the 2 GD line in 3 generations.
My questions would be first, what are the odds of this occurring, and second, what does this rapid? mutation mean to the Y's usefulness as a tracking method with this line?
Thanks for any input.
I am (37,2) with a guy who shares a patrilineal 5th great grandfather with me.

I wouldn't lose any sleep over your example.

Jack
Reply With Quote
  #4  
Old 9th July 2018, 06:34 AM
spruithean spruithean is online now
FTDNA Customer
 
Join Date: Dec 2008
Location: Canada
Posts: 674
I doubt it is a sign of anything surprising. I have a GD of 2 with a 3rd cousin 3 times removed. Mutations are random and there can even be back mutations in a few generations.
Reply With Quote
  #5  
Old 9th July 2018, 07:08 AM
Jim Barrett Jim Barrett is offline
R-BY39877
 
Join Date: Apr 2003
Location: Timpson, TX
Posts: 2,268
Quote:
Originally Posted by stev703 View Post
Hi, I have 2 kits from men who are 2nd cousins. They share a common Great Grandfather. One of the cousins matches another known descendant of the same great grandfather at 0 GD at 111 markers. The other of the two cousins shows 2 GD at 111 markers. Evidently there were two mutations in the 2 GD line in 3 generations.
My questions would be first, what are the odds of this occurring, and second, what does this rapid? mutation mean to the Y's usefulness as a tracking method with this line?
Thanks for any input.
Father and son can be a genetic distance of one on just 25 markers or even 12 markers.
Reply With Quote
  #6  
Old 9th July 2018, 09:51 AM
John McCoy John McCoy is online now
FTDNA Customer
 
Join Date: Nov 2013
Posts: 699
It may be possible to estimate the odds, because for most STR's there are (somewhere!) estimates of the mutation rate. However, interpreting individual cases will inevitably come down to "how lucky you are that a mutation occurred in THIS generation". The mutation rate tells you something about what to expect for populations, and roughly how often to expect a mutation in an individual case. But even if a mutation were extremely unlikely, that does not raise alarm bells if you happen to find one.

Also, there's no reason to believe that the actual mutation rate is the same for all individuals, since the molecular machinery believed to be involved in STR mutations (DNA replication and repair) is itself under genetic control.

As mentioned in this thread, there are families where different branches happened to end up with one or more STR mutations that have remained stable through several generations, and that has allowed these families to assign problem descendants to a particular branch.
Reply With Quote
  #7  
Old 9th July 2018, 11:03 AM
spruithean spruithean is online now
FTDNA Customer
 
Join Date: Dec 2008
Location: Canada
Posts: 674
Quote:
Originally Posted by John McCoy View Post
As mentioned in this thread, there are families where different branches happened to end up with one or more STR mutations that have remained stable through several generations, and that has allowed these families to assign problem descendants to a particular branch.
Precisely, I think there are a number of family projects that have established various branches of their respective family based on STR variations and private terminal SNPs. It is really quite interesting!
Reply With Quote
  #8  
Old 9th July 2018, 12:46 PM
John McCoy John McCoy is online now
FTDNA Customer
 
Join Date: Nov 2013
Posts: 699
Poster child for family with multiple SNP mutations defining multiple branches seems to be Buchanan (see Big Tree, R-L1335 branch, http://www.ytree.net/DisplayTree.php?blockID=9), with at least 21 distinct branches defined by SNP's, plus a branch from within the Buchanan haplotree that became McAusland and similar spellings. A stunning accomplishment to shepherd so many Buchanan kits through a very detailed analysis at considerable cost.
Reply With Quote
  #9  
Old 9th July 2018, 01:05 PM
MoberlyDrake MoberlyDrake is offline
mtDNA: T2b5 | Y-DNA: J-M172
 
Join Date: May 2010
Posts: 1,533
My first cousin is a GD of 2 with his 3rd cousin once removed. My 3rd great-grandfather had 2 sons and it appears that there was one mutation in each line. This gives my 1st cousin and his 3rd cousin once removed a GD of 1 with most of their matches who have the same surname, but a GD of 2 with each other though they are more closely related to each other than they are to their matches with a GD of 1.
Reply With Quote
Reply

Bookmarks


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Only 25 generations? jötunn Paternal Lineage (Y-DNA STR) Basics 6 19th February 2018 02:05 AM
Relating number of mutations to number of generations morvoren Paternal Lineage (Y-DNA STR) Advanced 4 27th September 2016 10:38 AM
how far Y-dna go in generations? hamad Y-DNA Haplogroups & SNPs Basics 2 14th June 2016 07:18 AM
How many generations? Native mtDNA - Advanced Topics 2 17th June 2006 05:59 PM
Generations Margbond DNA and Genealogy for Beginners 1 16th March 2006 09:37 AM


All times are GMT -5. The time now is 10:40 AM.


Family Tree DNA - World Headquarters

1445 North Loop West, Suite 820
Houston, Texas 77008, USA

Phone: (713) 868-1438 | Fax: (832) 201-7147
Copyright 2001-2010 Genealogy by Genetics, Ltd.
Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.