Go Back   Family Tree DNA Forums > General Interest > DNA and Genealogy for Beginners

DNA and Genealogy for Beginners Everything you wanted to know about DNA and Genealogy but didn't know where to ask. This board is open to customers and visitors.

Reply
 
Thread Tools Display Modes
  #1  
Old 10th February 2018, 05:55 PM
Chico Chico is offline
FTDNA Customer
 
Join Date: Dec 2017
Posts: 6
Question SNP Poor Regions

Hi - I have several "SNP Poor Region, not tested for family finder" light gray sections on my Chromosome Browser results.

What exactly does that mean (and I already am guessing there are not a lot of SNP's in those sections). Is this common to everyone (it happens to others, same locations, different locations, lesser or greater extent)? Would I have those same results if I took this test with other companies, or retested with FTDNA (meaning it is a permanent situation)? Or was there something specific to this test, and if so, what could it be?

Thanks for helping me understand this detail.
Chico -
Reply With Quote
  #2  
Old 10th February 2018, 06:32 PM
loobster loobster is offline
FTDNA Customer
 
Join Date: Feb 2012
Posts: 554
I think the gray / SNP Poor regions are a general, across-the board thing - do not think they went, "oh, this is where you personally happen to have a SNP Poor area" - they know that will be a SNP Poor area, so do not look there.
Reply With Quote
  #3  
Old 10th February 2018, 07:14 PM
John McCoy John McCoy is offline
FTDNA Customer
 
Join Date: Nov 2013
Posts: 566
Whether the "SNP-poor" regions matter with respect to detecting matching segments depends on the recombinational length of the region itself, as expressed in centiMorgans. If the length of the region measured in this way is very short (say, much less than 1 cM), the probability that a recombinational event (a crossover) within the region could have happened and not be detected by the matching algorithm is small. On the other hand, if the distance between SNP's is on the order of 5 cM or more, the probability of an unnoticed crossover is (by definition of the centiMorgan unit) much higher.

One sort of "SNP-poor" region is the neighborhood of the centromeres. For the human autosomes, most of these uncharted centromere regions are extremely short in terms of recombination (much less than 1 cM), so it should be safe to ignore any warnings about "SNP-poverty" for genealogical purposes, even though the length of the same regions in millions of base pairs may seem high. Whether a segment is passed on to the next generation depends on the probability of recombination, and not on the length of the segment in millions of base pairs.
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 Off
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Location of X centromere and poor regions? orrac Family Finder Advanced Topics 4 14th April 2017 11:43 AM
New Font? My poor eyes... Petra Grumbles & Gripes 11 30th December 2015 05:55 PM
SNP Poor Regions DavdJ Family Finder Advanced Topics 2 27th September 2013 12:45 PM
Poor SNP Regions EdwardRHill Family Finder Advanced Topics 0 24th November 2012 12:42 AM
Poor 12-marker matches but good 37 and 67? neil_soton DNA and Genealogy for Beginners 3 6th October 2010 04:05 AM


All times are GMT -5. The time now is 10:41 PM.


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.