Author Topic: X chromosome - confusion? False negative?  (Read 461 times)

Offline gazania

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X chromosome - confusion? False negative?
« on: Sunday 04 February 18 06:14 GMT (UK) »
I have tested autosomal with FTDNA.  I have recently been contacted by a match, I shall call her MA.  Our extremely well documented paper research confirms our links.  We have a common male ancestor, with a very rare surname, I shall call GC.  Our paper trail confirms she is a third cousin, once removed from GC.  We share 47 centimorgans and long block 16.  So far so good.

MA is descended directly along the female line, from the youngest daughter and only surviving child of GC,  from his first marriage.  I ( a female) am descended from the son of GC 's second marriage.  In other words MA is descended from my ggrandfather's half sister.

MA and her family still live within the vicinity of the small town in Yorkshire.

The problem I have:

MA and I share the X chromosome at 5.51cms.  (So does her daughter but at a smaller level)

According to my charting of relationships and the Xchromosome, MA could get the X from our common ancestor GC through his daughter.  But not me as I am descended from his son, albeit from a second marriage.

My confusion arises from how can this be? or is the 5.51cms too small to worry about? or is there something else going on? or I have misunderstood the whole concept?

I do hope this makes sense to read.  Thank you, Gazania
ALDERMAN, Bucks
BELK, Yorkshire, London
CARLING, Bedfordshire
CUNDITH,CUNDILL, Yorkshire, PALIN. Lincolnshire
FOX, Essex; Camberwell Surrey
LANE, Cork IE;Askeaton LIM, Liverpool, Clifton, Bristol
VOLLER, Surrey
WALL Clonlara Co Clare Ireland
WAREHAM, Esher, Surrey; London
WINCH, Surrey

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Offline rsel

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Re: X chromosome - confusion? False negative?
« Reply #1 on: Sunday 04 February 18 06:23 GMT (UK) »
Hi Gazania, I am no expert by any means, but everything I have read suggests that anything less than 7cm is to small to worry about.

Richard
Sellens - Sussex
Newham - Surrey
Wellington - Dagenham, Essex
Camp - South Essex
Wren - Essex
Livermore - Essex
Wane - Essex
Fisk - Essex / Suffolk
Bailey/Bayley - Sussex
Newton - Sussex
Funnell - Sussex
Streeter - Sussex
Coates - Sussex
Maisey - Surrey

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Offline gazania

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Re: X chromosome - confusion? False negative?
« Reply #2 on: Sunday 04 February 18 06:36 GMT (UK) »
Thanks, Richard, for your prompt reply.  My thoughts too.  DNA and random selection were never meant to be easy. Gazania
ALDERMAN, Bucks
BELK, Yorkshire, London
CARLING, Bedfordshire
CUNDITH,CUNDILL, Yorkshire, PALIN. Lincolnshire
FOX, Essex; Camberwell Surrey
LANE, Cork IE;Askeaton LIM, Liverpool, Clifton, Bristol
VOLLER, Surrey
WALL Clonlara Co Clare Ireland
WAREHAM, Esher, Surrey; London
WINCH, Surrey

Offline Ruskie

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Re: X chromosome - confusion? False negative?
« Reply #3 on: Sunday 04 February 18 07:18 GMT (UK) »
I was recently told that an X match under 20 cM could be a false positive.  :-\

Offline gazania

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Re: X chromosome - confusion? False negative?
« Reply #4 on: Sunday 04 February 18 11:06 GMT (UK) »
Ruskie, thanks for the information.  I shall be wary now about interpreting X matches.  Gazania
ALDERMAN, Bucks
BELK, Yorkshire, London
CARLING, Bedfordshire
CUNDITH,CUNDILL, Yorkshire, PALIN. Lincolnshire
FOX, Essex; Camberwell Surrey
LANE, Cork IE;Askeaton LIM, Liverpool, Clifton, Bristol
VOLLER, Surrey
WALL Clonlara Co Clare Ireland
WAREHAM, Esher, Surrey; London
WINCH, Surrey

Offline xinia

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Re: X chromosome - confusion? False negative?
« Reply #5 on: Sunday 04 February 18 11:32 GMT (UK) »
This post makes me realise ---(I thought so anyway )  that me sending off for DNA thingymibob... was a waste of time.

AS reading this I haven't got the first 'clue' what the heck you are talking about and doubt now that this tired (no space left) brain will ever comprehend.. :) :)

I need to quickly get to know someone who  totally understands and can then explain to me in simple layman's terms.... 

sorry  to interrupt.

xin

Offline Ruskie

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Re: X chromosome - confusion? False negative?
« Reply #6 on: Sunday 04 February 18 11:47 GMT (UK) »
Not a waste of time Xin. Even if you don't find loads of new cousins, it is a bit of fun and very interesting. Which test did you take?

I think many of us have taken tests without being able to make sense of the results. It's a bit of a learning curve that's for sure.  ;)

Ask for help interpreting your results (in layman's terms) when they arrive.  :)

Offline gazania

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Re: X chromosome - confusion? False negative?
« Reply #7 on: Sunday 04 February 18 11:50 GMT (UK) »
Hi Xin,

I am with you, Xin.  At least I have found a couple of new relatives which my paper trail confirms and we communicate the old fashioned way.  But I have a lot of "matches" which fall into the false negative realm, ie false hope and there is nothing in the paper trail.

The above case is the exception.  The match well and truly fits into our paper trail but the DNA (X chromosome in this case) does not and the measurement is too low anyway.  But I am so pleased that I made contact with the match.  Clear as Mud?  Best wishes, Gazania
ALDERMAN, Bucks
BELK, Yorkshire, London
CARLING, Bedfordshire
CUNDITH,CUNDILL, Yorkshire, PALIN. Lincolnshire
FOX, Essex; Camberwell Surrey
LANE, Cork IE;Askeaton LIM, Liverpool, Clifton, Bristol
VOLLER, Surrey
WALL Clonlara Co Clare Ireland
WAREHAM, Esher, Surrey; London
WINCH, Surrey