Go Back   Family Tree DNA Forums > The X-Chromosome > X-DNA Basics

X-DNA Basics This forum is for newbie topics about the X-Chromosome. All may view this forum, but you must register and sign in to post.

Reply
 
Thread Tools Display Modes
  #1  
Old 5th May 2017, 07:13 AM
MBC MBC is offline
FTDNA Customer
 
Join Date: Apr 2017
Posts: 14
Question X-DNA question - siblings same X as me?

Hello,

My question has to do with the X-DNA. Since I (female) inherited X from both of my parents, wouldn't my 2 sisters have inherited the same 2 X's? I do not have any brothers.

I know that I am not as advanced as many are in this. Thank you for taking the time to help me to understand!
Reply With Quote
  #2  
Old 5th May 2017, 07:20 AM
MBC MBC is offline
FTDNA Customer
 
Join Date: Apr 2017
Posts: 14
I think I have figured out some more about this.

The X from our mother would be "mixed" - so our X would not necessarily match. The X that we received from father would be the same, but not the part from mother.

Since neither father or mother is living, we cannot know exactly what part is matching.

Or, as sisters, we compare our X, and we can determine the part that we each received from father? Each of us would match exactly (all 3 matching) at the part we received from father, right?

Thanks!
Reply With Quote
  #3  
Old 5th May 2017, 09:12 AM
prairielad prairielad is offline
FTDNA Customer
 
Join Date: Feb 2011
Location: Canada
Posts: 1,690
Females have two X's
one from father that will be identical as father only had one and it is passed on intact (no recombination) to all daughters.
and one from mother that is a random recombination of her two.

Chromosome browsers merge the two (each chromosome comes in pairs, a maternal and a paternal)

Utilizing a site called Gedmatch and using their X one to one compare with graphic you can see which area of X sisters are matching on their maternal X chromosome, as it will be shown as full base pair matching(green), which means you are matching on your paternal X as well as your maternal X
Sisters will match also along the entire length of X due to having the identical X from father (half base pair matching, yellow)
Reply With Quote
  #4  
Old 5th May 2017, 09:37 AM
MBC MBC is offline
FTDNA Customer
 
Join Date: Apr 2017
Posts: 14
Thank you!
Reply With Quote
  #5  
Old 9th May 2017, 02:00 PM
MBC MBC is offline
FTDNA Customer
 
Join Date: Apr 2017
Posts: 14
prairielad,

Ok. I looked at the X one-to-one match. This is what I see:

Chr Start Location End Location Centimorgans(cM) SNPs
X 2,321 154,886,292 194.8 15,841

The full base pair matching (green)is shown on the top line - most of it is green, but some of it is yellow (in the middle part of the line is mostly where it is yellow).
The dark blue - matching segments greater than 7 cM - is a solid "bottom" line.

So, the yellow is where we both match on the paternal side?

Thanks!
Reply With Quote
  #6  
Old 9th May 2017, 02:08 PM
MBC MBC is offline
FTDNA Customer
 
Join Date: Apr 2017
Posts: 14
Hello again,

One further question.

Since there are 3 of us sisters, would the X that we received from father (should be the same for all of us) be the area where we all match in yellow?

It is interesting because our graph does not show the same areas of yellow.

Thanks!
Reply With Quote
  #7  
Old 9th May 2017, 03:26 PM
John McCoy John McCoy is offline
FTDNA Customer
 
Join Date: Nov 2013
Posts: 505
For the graphics option on the GEDmatch web site, the color coding on the upper part of the bar is YELLOW for "half match". Half match means you match ONE copy of the chromosome (X chromosome, in this case) at that location. GREEN color coding means that you match BOTH copies of the chromosome at that location. So GREEN is a stronger match than YELLOW.

So, 3 daughters of the same father will match AT LEAST
YELLOW over the entire length of the X chromosome, because they each got the same X chromosome from their father.

The same 3 daughters, if they also have the same mother, will have SOME sections in GREEN, because they match not only on the X they each got from their father, but also on some part of the X chromosome that they received from their mother. Because of recombination, each daughter will probably get a different combination of segments drawn from their mother's 2 X chromosomes, but there will be some overlap. (If you were not paying attention in biology class and have forgotten how recombination works, now's a good time to do some reading!)
Reply With Quote
  #8  
Old 9th May 2017, 06:29 PM
prairielad prairielad is offline
FTDNA Customer
 
Join Date: Feb 2011
Location: Canada
Posts: 1,690
The following may help you understand the yellow and green at gedmatch

Chromosome browsers merge the maternal and paternal chromosome pairs into one. Benefit with gedmatch they show the sections of Half base pair and Full base pair matching (matching on one chromosome of the pair or both)

On Gedmatch, depending on testing company, some test the PAR regions of X, they are located at the beginning and end of the X chromosomes. These are sections can undergo recombination in the father when X is passed onto daughter. These sections can swab segments with the Y Chromosome. Sisters may show as a non match along these sections (red)

PAR Region explanations
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2435358/
https://en.wikipedia.org/wiki/Pseudoautosomal_region
Attached Images
File Type: png X chromosome.png (20.7 KB, 9 views)

Last edited by prairielad; 9th May 2017 at 06:38 PM.
Reply With Quote
  #9  
Old 10th May 2017, 07:20 AM
MBC MBC is offline
FTDNA Customer
 
Join Date: Apr 2017
Posts: 14
Thank you to both of you for good and simple explanations!

I am understanding more and more!
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
Tests for Siblings McGarrahanK DNA and Genealogy for Beginners 4 19th January 2017 12:43 AM
Having 1/2 siblings test Sara291 Adoptees Forum 2 3rd August 2016 07:42 AM
Half-Siblings? Wolfie DNA and Genealogy for Beginners 4 12th July 2014 06:39 AM
half siblings similligan Family Finder Advanced Topics 19 7th December 2013 08:49 PM
Siblings super8mm Family Finder Advanced Topics 11 20th January 2012 03:42 PM


All times are GMT -5. The time now is 12:18 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 - 2017, Jelsoft Enterprises Ltd.