Author Topic: High cM for a 3rd cousin  (Read 946 times)

Offline sugarfizzle

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Re: High cM for a 3rd cousin
« Reply #9 on: Monday 05 November 18 07:45 GMT (UK) »
I know that DNA is not an exact science, but surely it is impossible to inherit more than 6.25% DNA from 2G grandparents (I am very much open to correction here).

AncestryDNA use the total number of cM as 3475.

That said, you can't share more than 3475 x 6.25%, which is equal to approx 217.2 cM with a 3rd cousin (Blaine Bettinger says 217 cM, as you say)

By that reasoning, I would suggest a bit of extra marital relationship on the side at some stage. Or, perhaps, more likely, incest.
Or a mistake in one of the trees!

My reasonings may be faulty, happy enough if anyone corrects me!

Regards Margaret

Modified. Or have Ancestry got it wrong? If your match uploads elsewhere, you will be able to see whether they agree or not.
STEER, mainly Surrey, Kent; PINNOCKS/HAINES, Gosport, Hants; BARKER, mainly Broadwater, Sussex; Gosport, Hampshire; LAVERSUCH, Micheldever, Hampshire; WESTALL, London, Reading, Berks; HYDE, Croydon, Surrey; BRIGDEN, Hadlow, Kent and London; TUTHILL/STEPHENS, London
WILKINSON, Leeds, Yorkshire and Liverpool; WILLIAMSON, Liverpool; BEARE, Yeovil, Somerset; ALLEN, Kent and London; GORST, Liverpool; HOYLE, mainly Leeds, Yorkshire

Census Information is Crown Copyright, from www.nationalarchives.go

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Offline Mart 'n' Al

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Re: High cM for a 3rd cousin
« Reply #10 on: Monday 05 November 18 08:16 GMT (UK) »
6.25% is the statistical average. In theory it could be as much as 50%. Although it is unlikely, it is statistically possible but if you have 100 coloured marbles, half blue and half red, all the red ones could be passed down to the Next Generation and continually after that. It is unlikely but statistically possible.

Martin
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FT-DNA Kit B388093

Names:
Loughborough and Loughbrough, (London, Hull, Pirton, Durham & Hartlepool);
Watson, (Bedlington, Jarrow & Hartlepool);
Ballard & Glassop (E. London); 
Leggett (Corton, Scarborough, Hartlepool); 
Young, Adamson & Wilson, (Hartlepool). 

I use GRAMPS v5.0 software. 

My ancestors are probably turning in their graves, not that I can actually find any of them.

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Offline Gadget

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Re: High cM for a 3rd cousin
« Reply #11 on: Monday 05 November 18 10:12 GMT (UK) »
Thanks for latest comments. I have done a pretty thorough paper trail check on that line as it's the most heavily populated! This line has been thoroughly researched by many cousins and we've all checked each others' work   ;D

After the 2xgreats' generation, the offspring went their separate ways and seem never to be in the same place (Wales-Yorkshire-Staffordshire). Also the dates don't fit. At that generation or before, any sexual encounters  between close relatives would likely show up in the cMs of the other cousins.

I'm currently trying to contact another cousin of that family/generation to find out how they match. Also, I'm trying to investigate more about the ancestry of AS's husband's line. It could be that the husband's line is related to one of my grandmother's lines pre-1770/90; possibly a Cash-Williams link.

Gadget
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Offline Gadget

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Re: High cM for a 3rd cousin
« Reply #12 on: Monday 05 November 18 10:44 GMT (UK) »
I've just checked with b2 (only made contact a month ago!) in my diagram above and she is my 3rd cousin once removed, so have adjusted the diagram.

 
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Offline sugarfizzle

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Re: High cM for a 3rd cousin
« Reply #13 on: Monday 05 November 18 14:11 GMT (UK) »
6.25% is the statistical average. In theory it could be as much as 50%. Although it is unlikely, it is statistically possible but if you have 100 coloured marbles, half blue and half red, all the red ones could be passed down to the Next Generation and continually after that. It is unlikely but statistically possible.

Martin

Thanks, Martin. I thought as I was writing that something had gone wrong with my reasoning, which was why I said twice that I was open to correction!

My brain doesn't get into gear sometimes.

Regards Margaret

Modified:
Taking it to the next generation -

https://www.google.co.uk/amp/s/amp.reddit.com/r/23andme/comments/9cv78s/do_we_inherit_5050_from_our_parents/#ampf=undefined
visualtim Sep 4, 2018, 8:17 AM

Here's a simple analogy:

You have 100 blue marbles in a jar on your left: this represents your father's genome. You 100 red marbles on your right: these are your mother's. Close your eyes and pick 50 marbles from each jar and put them in a new jar: your jar.

Now count them. It's obvious you should have 50 red and 50 blue marbles in your jar.

Now, you have a kid. Close your eyes and reach into YOUR jar of red and blue marbles. Take out 50. Now open your eyes and count how many of red and blue marbles you gave to your child. In an ideal world, it's 25 blue and 25 red. But since it's random, it could be 20/30 or 26/24. It's even possible, but highly improbable, to have 50/0.

Regards Margaret
STEER, mainly Surrey, Kent; PINNOCKS/HAINES, Gosport, Hants; BARKER, mainly Broadwater, Sussex; Gosport, Hampshire; LAVERSUCH, Micheldever, Hampshire; WESTALL, London, Reading, Berks; HYDE, Croydon, Surrey; BRIGDEN, Hadlow, Kent and London; TUTHILL/STEPHENS, London
WILKINSON, Leeds, Yorkshire and Liverpool; WILLIAMSON, Liverpool; BEARE, Yeovil, Somerset; ALLEN, Kent and London; GORST, Liverpool; HOYLE, mainly Leeds, Yorkshire

Census Information is Crown Copyright, from www.nationalarchives.go

Offline rsel

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Re: High cM for a 3rd cousin
« Reply #14 on: Monday 05 November 18 18:43 GMT (UK) »
Have you looked at this website ?  https://dnapainter.com/tools/sharedcmv4  one of the useful features is that you can enter the number of shared cM's and it will give you the percentages of likely hood for each direct relationship.

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

Offline Gadget

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Re: High cM for a 3rd cousin
« Reply #15 on: Monday 05 November 18 20:01 GMT (UK) »
 Thanks,Richard. I use it often and you must have missed my reference to it in my original post.


The Bettinger chart  suggests a range of 0-217 for 3rd cousins, and puts 292 as way out of the expected range.  Do any members have similar measures for 3rd cousins?

Gadget

Census &  BMD information Crown Copyright www.nationalarchives.gov.uk and GROS - www.scotlandspeople.gov.uk

Offline rsel

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Re: High cM for a 3rd cousin
« Reply #16 on: Monday 05 November 18 22:02 GMT (UK) »
Thanks,Richard. I use it often and you must have missed my reference to it in my original post.
It didnt tie it to this website :-) but it was more the likelyhood percentages that i was really refering to rather than just the chart.
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

Offline Gadget

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Re: High cM for a 3rd cousin
« Reply #17 on: Sunday 30 December 18 13:21 GMT (UK) »
Update:

After many weeks of searching for a second connection that didn't involve the other two 3rd cousins, I've finally found the explanation  :)

The main relationship was through my father's father's mother and siblings (my grt grandmother) . I now find that my father's mother's grandmother was related to his mother's paternal line, as in this:

It could be that the husband's line is related to one of my grandmother's lines pre-1770/90; possibly a Cash-Williams link.

I think it's dble 3rd cousin


Gadget

Census &  BMD information Crown Copyright www.nationalarchives.gov.uk and GROS - www.scotlandspeople.gov.uk