1st cousin or half sibling confusions

[bradalucas]

I have recently  researched a situation that is growing more confusing the more I look into it.  Basically my mothers dna results came back and after uploading to gedcom discovered a match sharing 1505cM. Contacted person found out it was child to her presumed fathers brother. With that much shared DNA they are appearing to be more linked than 1st cousins? Also the x match tool on gedcom I have attached for review. Does this make any sense? We know it's not a double cousin situation and leaning towards half sibling. Also awaiting some other family members to test a nephew and another presumed brother. The match is also a female if that helps for x comparison I was assuming it should show 50% if cousins but this showimg something differently?

[melba_schmelba]

I have recently  researched a situation that is growing more confusing the more I look into it.  Basically my mothers dna results came back and after uploading to gedcom discovered a match sharing 1505cM. Contacted person found out it was child to her presumed fathers brother. With that much shared DNA they are appearing to be more linked than 1st cousins? Also the x match tool on gedcom I have attached for review. Does this make any sense? We know it's not a double cousin situation and leaning towards half sibling. Also awaiting some other family members to test a nephew and another presumed brother. The match is also a female if that helps for x comparison I was assuming it should show 50% if cousins but this showimg something differently?

I don't have any experience with the X tool, but I presume that only works on kits that analyse the Mitochondrial DNA, like 23andme and LivingDNA? I assume the test you've shown above would show that those two people have the same or fairly closely maternal line. I am not sure whether it means you are close as in the last 500 years or even 2000 though! Hope someone else can be more helpful  .

[Gadget]

Using the painter tool, the shared DNA suggests

Relationship probabilities (based on stats from The DNA Geek)

    98.58%  Grandparent Aunt / Uncle      Half Sibling Niece / Nephew      Grandchild
    1.42%   Great-Grandparent     Great-Grandchild     Half Aunt / Uncle     Half Niece / Nephew  1C    Great-Aunt / Uncle   Great-Niece/Nephew

I'm not sure how Gedmatch get's the X chromosome details from autosomal testing but I also get X matches (with my ch23 XX) on the site.


Gadget

[melba_schmelba]

Using the painter tool, the shared DNA suggests

Relationship probabilities (based on stats from The DNA Geek)

    98.58%  Grandparent Aunt / Uncle      Half Sibling Niece / Nephew      Grandchild
    1.42%   Great-Grandparent     Great-Grandchild     Half Aunt / Uncle     Half Niece / Nephew  1C    Great-Aunt / Uncle   Great-Niece/Nephew

I'm not sure how Gedmatch get's the X chromosome details from autosomal testing but I also get X matches (with my ch23 XX) on the site.


Gadget

Hmmm you're right . I have tested both my parent's kits to their 10 closest matches on GEDMATCH, and one matched, the closest match on my father's side who I believe share a maternal line. I knew that ancestry kits had some Y-DNA info as you can get a guesstimate for your haplogroup using the Morley DNA site

https://geneticgenealogist-net.nomorecoldcases.com/2017/08/updated-method-to-get-ydna-haplogroup.html
https://ytree.morleydna.com/

But as far as I knew ancestry kits didn't contain enough X-DNA to give a maternal haplogroup, but perhaps things changed with a new chip ?

 

[Gadget]

Another thought because the painter tool doesn't really show double cousinship.  I had yet another double one come up this morning - the match was descended from two of my lines. Luckily she had a tree and it was accurate - I even remember some of the people on it 

Gadget

[pughcd]

Hi Melba_Schmelba ,

Sorry but you are falling into the trap of equating the X-chromosome with the mitochondrial DNA.

The mitochondria is a circular organelle found in the cytoplasm of all cells. It is 16,569 base pairs in length in humans. The mitochondria are involved with day to day energy production at the cellular level. During reproduction, the female ovum or egg contributes the majority of the cytoplasm as well as the female chromosomes, whilst the male usually just provides the male chromosome to the zygote. Thus in general terms the vast majority of cytoplasmic mitochondria develops from the initial female contribution of cytoplasm to the new zygote (Introduction to Genetic Analysis, Griffiths et al. 2015, Freeman Press). The mitochondrial DNA can be compared to a reference DNA  and the subtle differences can allow scientists to classify the mtDNA into haplogroups. These haplogroups can be displayed as  a phylogenetic tree based on the historic development of the genetic mutations of the DNA that come to represent new haplogroups.

This is all completely different from the nuclear chromosomes, which include the sex chromosomes X and Y. These are inherited as pairs, with one chromosome  coming from the male and the other from the female. Thus chromosome 1 pair has a male and female chain, chromosome 2 pair  has one male and one female chain etc up to chromosome 22. These makes up the autosomal DNA.  Then the 23rd chromosome pair are the sex chromosomes; made up of XX (women) or XY (men).

At the AncestryDNA.co.uk website it does state that " The Ancestry DNA test analyzes your entire genome- all 23 pairs of chromosomes.." Consequently, if you then transfer the raw data to GEDmatch you will be able to utilise the X chromosome matching tools, although Ancestry does not report this data specifically within it's pages.

So to sum up mitochondrial DNA is found in the cytoplasm of cells and the 23 pairs of autosomal and sex chromosomes  are found in the cell nucleus. Thus X chromosome  inheritance has nothing to do with mitochondrial DNA. Hope that is clear but I am happy to follow up further.

The brilliant blog "DNA Explained" has several good pages on X chromosome and mtDNA https://dna-explained.com/2018/02/07/who-tests-the-x-chromosome/ and
https://dna-explained.com/2019/01/10/mitochondrial-dna-bulldozes-brick-wall/

Regards,
pughcd

[Gadget]

Hi pughcd

I think you must have missed melba's answer to me  (Reply #3) when she said:

Hmmm you're right .

...............

But as far as I knew ancestry kits didn't contain enough X-DNA to give a maternal haplogroup, but perhaps things changed with a new chip ?

[pughcd]

Hi Gadget,

Indeed and it appears to confirm that there is some confusion here. Maternal haplogroups are defined by mutations on the mitochondrial DNA. This is nothing to do with the X chromosome.

pughcd

[Gadget]

Agree - mine was just a simple Ancestry autosomal test  but Gedmatch found quite a few X matches and, as I'm female, they could come from either my mother or father.