Author Topic: Number/length of shared segments, number of chromosomes  (Read 948 times)

Offline decor

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Number/length of shared segments, number of chromosomes
« on: Wednesday 08 December 21 20:29 GMT (UK) »
Hello everyone

Just trying to deepen my understanding of DNA and have a few questions for better-informed people than myself, specifically relating to one of my mother's matches on MyHeritage.

On MyHeritage one of my mother's closest matches is her maternal cousin, let's call her T.R. They share 881 centimorgans (which is to be expected) and have 27 shared segments split over 16 chromosomes, the largest segment being 125.8cM.

Both my mother and T.R. also have a match with an unidentified person (no personal information or family tree and hasn't replied to message).
T.R. shares 839.2cM with this match.
My mother shares 1062.0cM with this match. They have 38 shared segments split over 20 chromosomes, the largest segment being 74.1cM.
All three of them have 11 triangulated segments.

I suppose my question is the following: Is it common to shared 1062.cM with someone, spread over so many segments on almost all chromosomes?

Looking forward to reading your replies. Maybe I'm overthinking it all.  :D


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Offline Galium

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Re: Number/length of shared segments, number of chromosomes
« Reply #1 on: Wednesday 08 December 21 21:38 GMT (UK) »
Have you had a look at anything like this chart - which shows likely relationships for a given number of shared centimorgans?

https://dnapainter.com/tools/sharedcmv4
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Offline Heb66

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Re: Number/length of shared segments, number of chromosomes
« Reply #2 on: Wednesday 08 December 21 21:55 GMT (UK) »
Hi Decor,
I have a 1062 centimorgan match on one of my search angel projects I've worked on in the past.
The proven relationship is a daugter of a half sibling to that match.
Hope this helps.....
Helen.
P.S The centimorgan ranges of the three half siblings varied enormously...the birth year span was from 1929 to 1936. The daughter was born in 1963.
Payne, Woodchester Glos / Kings Norton Worcs.
Luker, Glos.
Davis, Smith, Evans, Lockstone,Latham, Kings Stanley.
Bingham; Stroud, Glos.
Gore: Glos/ Plymouth.
Rodway: Woodchester, Glos. Wanted Henry Rodway born 1849. Missing since 1881.
Morgan: Nettleton Wilts / Stroud Glos.

Offline Gadget

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Re: Number/length of shared segments, number of chromosomes
« Reply #3 on: Wednesday 08 December 21 22:20 GMT (UK) »
Quote
suppose my question is the following: Is it common to shared 1062.cM with someone, spread over so many segments on almost all chromosomes?

This is a close relationship. I share similar amounts ( circa 1000 +/-) with my great nephew and niece. Also matches on many segments. 

Using the calculator link given by Galium, the person could also be a close half relative.
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Offline decor

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Re: Number/length of shared segments, number of chromosomes
« Reply #4 on: Wednesday 08 December 21 23:26 GMT (UK) »
Thanks for all the replies.
I wasn't so much interested in the potential relationship, but the number of shared segments on almost all chromosomes. Just wondered if they indicated anything, like multiple connections to the same person.

I wrote to the match and I'd be very happy if they replied but I'm not holding out hope.
And I don't want to open a can of worms in the family if there's some big secret.
From MyHeritage I can see the user is based in the UK (like my Mum), and his rough age and his empty tree has been given a surname. He has matches with people with roots in the same area as my mum. I did some digging and found a possible person on FreeBMD...and mapped out his tree. This individual would be a 5th cousin of my Mum's, so much more distant than 1062cM. So I'm wondering if there are multiple connections.
Whoever the match is they seem to have matches with other people from various branches of my mum's maternal ancestors, which would make sense if he was very closely related to my mum.

Now I'm rambling but one day I hope to uncover the mystery  ;D
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Offline Cell

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Re: Number/length of shared segments, number of chromosomes
« Reply #5 on: Sunday 12 December 21 11:50 GMT (UK) »
Hi
I am not sure if this helps,
but I can give you mine as a very good example ,which is very similar to your mother's situation , by being two full cousins and a match over 1000 like your mum's (and like your mum's - a lower shared match between my full first cousin to the same person).

I and my full first cousin have our dna on my heritage and so does a very high match at well over 1000cms to me  .


I to my full first cousin:
862 cm,
shared segments 35,
 largest  87


Me to our match
1,153 cm
Shared segments 37
Largest 95

My full first cousin to our match i( and is 100% definetely related exactly the same way as I am to our match!)
  Is only 713cm.


Our ( myself and my first cousin )  match up is our  parents half sibling ( that our family never knew about ,war baby situation)

I hope that helps  , probably not , but thought I'd give you a very similar example with how shared DNA  segments can  differ greatly between two full first cousins to the very same shared very close relative,  and I think maybe investigate  the match up being maybe a half uncle/ aunt to your mother and her cousin ( or a half nephew/niece)

Kind regards :)











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Offline decor

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Re: Number/length of shared segments, number of chromosomes
« Reply #6 on: Sunday 12 December 21 15:57 GMT (UK) »
Hi
I am not sure if this helps,
but I can give you mine as a very good example ,which is very similar to your mother's situation , by being two full cousins and a match over 1000 like your mum's (and like your mum's - a lower shared match between my full first cousin to the same person).

I and my full first cousin have our dna on my heritage and so does a very high match at well over 1000cms to me  .


I to my full first cousin:
862 cm,
shared segments 35,
 largest  87


Me to our match
1,153 cm
Shared segments 37
Largest 95

My full first cousin to our match i( and is 100% definetely related exactly the same way as I am to our match!)
  Is only 713cm.


Our ( myself and my first cousin )  match up is our  parents half sibling ( that our family never knew about ,war baby situation)

I hope that helps  , probably not , but thought I'd give you a very similar example with how shared DNA  segments can  differ greatly between two full first cousins to the very same shared very close relative,  and I think maybe investigate  the match up being maybe a half uncle/ aunt to your mother and her cousin ( or a half nephew/niece)

Kind regards :)

Thank you, Cell. That was very interesting to read - the DNA stuff is fascinating. I'll keep digging :)
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