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Mom matches me, my brother, some ICWs on same segment, but my brother and ICWs and I don't match

Mom matches me, my brother, some ICWs on same segment, but my brother and ICWs and I don't match

Posted: 28 Jun 2014 1:48PM GMT
Classification: Query
I've been coloring a particular segment on Genome Mate with great success. I'm very confident that this is working because I have generations of well-documented families nesting within each other and these segments are triangulating between my mom and my brother and various FTDNA and GEDMatch matches at various lengths, as expected.

So, it would make sense that all the ICWs at this segment should fall into this family, right? For instance (in Genome Mate shorthand):

On Chrome 12,

Cousin #1 matches Mom as a 6th cousin Butler from 0 - 12 for a total of 28.6 cMs
Cousin #1 matches Brother as a (I'm guessing 6th cousin 1x removed or something - I suck at cousin math!) Butler at 0 - 3 and 3 - 12 for a total of 28.6 cMs. This is actually showing as two different segments with a slight overlap. On the segment map, there is actually a tiny gap between the two segments. I chalk this up to scaling issues with Genome Mate's length of segment shorthand, so it doesn't concern me.

So, jumping over to my Genome Mate profile, I find that firstly, I do not match Cousin #1 or any other Butlers on Chrome 12 at any segment, yet I have other matches at 1 - 8 and 2 - 7 (between 13.7 and 19.6 cMs) that are ICW with my mother but not my brother.

So how can my mom match both my brother and me at the same segment but my brother and I do not match? How can my mom match me and the Butler cousins at the same segment, but I do not match the Butler cousins?

Is this also a scaling issue due to Genome Mate's length of segment shorthand? Are we getting down to SNP-level results at this point? It appears the segment in question has 700 SNPs.

700 SNPs is misleading (was Re: Mom matches me, my brother, some ICWs on same segment, but my brother and ICWs and I don't match

Posted: 28 Jun 2014 5:36PM GMT
Classification: Query
I cannot really address the majority of your post (brain fog moment as I am not understanding your description -- visual works better for me sometimes).

But I do want to address your last statement about the 700 SNPs. All of your matches from Gedmatch when done in a batch load into GenomeMate will show as 700 SNPS, even if the actual SNP value is 900 or 2000 or more. It has to do with the way that the copy and paste works from the mass data input. (I questioned the developer on the FB page about this). When doing a one-to-one match with a person I can see that the actual SNP value is higher normally. But if you just import the one-to-one match data it will not overwrite the 700 value. In order to get the correct value into GenomeMate (assuming you care about it -- I do -- I want the data in GenomeMate to be as accurate as possible) then you have to delete the offending segment match and then do the one-to-one comparison and reload the data. (Do not worry too much, any information on the relative info screen will not be lost -- only the segment data which you are reloading. Any segment specific data, such as identifying M/P/MGF/MGM/PGF/PGM or identified MRCA will be lost and will need to be re-keyed in.)

Elizabeth

Re: 700 SNPs is misleading (was Re: Mom matches me, my brother, some ICWs on same segment, but my brother and ICWs and I don't match

Posted: 28 Jun 2014 6:21PM GMT
Classification: Query
Elizabeth,

Thanks for the attempt. I was afraid I wasn't able to explain this as well as I'd like. I'll work on updating the SNPs when GedMatch is back up.

I've attached a visual - maybe that will help...I hope it's legible. Thanks!

Allie
Attachments:

Re: 700 SNPs is misleading (was Re: Mom matches me, my brother, some ICWs on same segment, but my brother and ICWs and I don't match

Posted: 28 Jun 2014 8:16PM GMT
Classification: Query
Allie,


At a given segment, your mother has two chromosomes to give, one that she received from her father (your maternal grandfather) and one that she received from her mother (your maternal grandmother). You didn't mention whether the Butler segment came from your maternal grandfather or your maternal grandmother's line. For the sake of discussion, let's say it's your maternal grandfather's line. Your brother's inheritance of the Butler segment came from that line, passed from your mother. However, your segment at that same location came from maternal grandmother. Your mother had a copy of both segments to pass along; one segment from one maternal grandparent went to you; your brother inherited the segment from the other maternal grandparent.

Your mother shares DNA with both of you at that segment; it's just a different piece of DNA.

For you not to match your brother at all at that particular segment suggests that you and your brother also inherited on your paternal side from different paternal grandparents (i.e. one of you inherited the paternal grandfather segment and one inherited the paternal grandmother segment). However, I'm sure you've inherited other segments in common, and other segments that are half-matches.

On gedmatch, the matches (in the graphic for one to one) are shown as red -no match of either maternal or paternally received chromosome at that segment, yellow (you share either the maternal or paternal chromosome at that segment but not both), or fully green (you and brother received the same maternal and paternal chromosomes at that segment).

When I compare myself to my siblings on gedmatch, I see some green (so I know that we got DNA at that segment from the same grandparent on my father's side and the same ( grandparent on my mother's side), Lots and Lots of yellow (we share from one grandparent's DNA), and also red (usually interspersed with very, very tiny yellow segments, basically meaning no match, meaning we inherited from different grandparents on both the maternal and paternal sides.)

I hope that makes sense. You won't be able to see that at genome mate because it doesn't show the half and full matches. Everything looks like a full match.

I think you can assume that you don't have the Butler DNA at that location (you're still a descendant of that common ancestor, it's just that the DNA washed out).

Re: 700 SNPs is misleading (was Re: Mom matches me, my brother, some ICWs on same segment, but my brother and ICWs and I don't match

Posted: 28 Jun 2014 8:23PM GMT
Classification: Query
"At a given segment, your mother has two chromosomes to give, one that she received from her father (your maternal grandfather) and one that she received from her mother (your maternal grandmother). You didn't mention whether the Butler segment came from your maternal grandfather or your maternal grandmother's line. For the sake of discussion, let's say it's your maternal grandfather's line. Your brother's inheritance of the Butler segment came from that line, passed from your mother. However, your segment at that same location came from maternal grandmother. Your mother had a copy of both segments to pass along; one segment from one maternal grandparent went to you; your brother inherited the segment from the other maternal grandparent."

Okay - this makes TOTAL sense to me, and something I've just not thought of until you pointed it out to me. In fact, the Butlers are on my Mom's paternal side...I'm getting her maternal piece of the pie on this segment.

This is also very helpful as I identify more segments. Thank you so much for the excellent explanation! I try to pay attention to the basics - but sometimes my eyes just glaze over. I done been schooled today!
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