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  #1  
Old 5th August 2017, 08:59 AM
AllynSpear AllynSpear is offline
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How can Dad share fewer cM with match than Son?

I did a family finder test a few years ago, and I just got my Dad's family finder results back today. There is one individual that comes up on my matches as a 2nd-4th cousin, with 60cM shared. On my Dad's matches, the same individual shows up, but as a 3rd-5th cousin, with 42 cM shared. This match does not come up on my mother's side. Now I am not a professional genetic genealogist, but I do have a basic understanding of molecular genetics. In my mind, the only possible mechanism for this is one of two things:

1. This match just randomly happens to have multiple small shared patches with my maternal side that in total add up to the additional 18 cM (in my mind unlikely).

2. This match is actually a distant relative on my Mom's side AND a 4th-ish cousin to my Dad.

Does anyone have any other suggestions or possible ways to figure this out??

Thanks,
Allyn
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  #2  
Old 5th August 2017, 09:52 AM
georgian1950 georgian1950 is online now
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Allyn,

the mother and father share a common ancestor, but the mother's DNA inherited from the ancestor is not enough to show up as a matching segment with the parameters being used. However when combined with the DNA from the husbands side passed down from the common ancestor, the son is able to show a larger matching segment than with the dad.

Jack Wyatt (T787998)
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  #3  
Old 5th August 2017, 11:12 AM
travers travers is offline
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Join Date: Oct 2010
Posts: 448
Quote:
Originally Posted by AllynSpear View Post
I did a family finder test a few years ago, and I just got my Dad's family finder results back today. There is one individual that comes up on my matches as a 2nd-4th cousin, with 60cM shared. On my Dad's matches, the same individual shows up, but as a 3rd-5th cousin, with 42 cM shared. This match does not come up on my mother's side. Now I am not a professional genetic genealogist, but I do have a basic understanding of molecular genetics. In my mind, the only possible mechanism for this is one of two things:

1. This match just randomly happens to have multiple small shared patches with my maternal side that in total add up to the additional 18 cM (in my mind unlikely).

2. This match is actually a distant relative on my Mom's side AND a 4th-ish cousin to my Dad.

Does anyone have any other suggestions or possible ways to figure this out??

Thanks,
Allyn
This is quite common and scenario #1 is the most likely explanation.
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  #4  
Old 5th August 2017, 11:30 AM
gatty gatty is offline
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Quote:
Originally Posted by georgian1950 View Post
Allyn,

the mother and father share a common ancestor, but the mother's DNA inherited from the ancestor is not enough to show up as a matching segment with the parameters being used. However when combined with the DNA from the husbands side passed down from the common ancestor, the son is able to show a larger matching segment than with the dad.

Jack Wyatt (T787998)
So if I am reading you correctly these would indicate my parents share a common ancestor ?
My father's cm in brackets.

Du 60 (43)
Boe 59(44)
Cla 55 (41)
Jo 53 (29)
Om 57 (44)
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  #5  
Old 5th August 2017, 12:13 PM
georgian1950 georgian1950 is online now
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Quote:
Originally Posted by gatty View Post
So if I am reading you correctly these would indicate my parents share a common ancestor ?
My father's cm in brackets.

Du 60 (43)
Boe 59(44)
Cla 55 (41)
Jo 53 (29)
Om 57 (44)
I have found that most parents are related within the past 300 years, regardless of what their child or whoever believes. This usually holds even if the parents are from different parts of the world.

If one goes back say eight generations, how can that person possibly know where all 256 lines go. If the person knows for sure, why bother with autosomal DNA testing?

Jack Wyatt
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