RootsChat.Com
General => Ancestral Family Tree DNA Testing => Topic started by: mona lisa on Friday 03 July 20 23:10 BST (UK)
-
Is a DNA match of say 7 cms 1 DNA segment of any value in ancestor matches ?
-
It can be. I have a few matches of 6cMs and have traced them to common ancestors.
See: https://dnapainter.com/tools/sharedcmv4
for possible relationships.
Gadget
-
Much appreciated Gadget......information very helpful!
-
I don't usually get interested in a 7cM match, but if they're matching a few of the known cousins I really like to have a better look at chromosome level, so NOT at Ancestry.
The extended family has had some breakthroughs with these very small matches from being able to see 'where' (on the chromosome) they're matching us, and who else these segments are shared with. Actually, at Ancestry you often don't notice them, because if they share under 20cM with all your known cousins you won't spot them. One of the best ones appeared quite some way down the page at Gedmatch, but when I clicked on her 11 known descendants of my gtgtgtgt-grandparents were in her top 15 matches. Turns out she is descended from my gtgtgtgt-grandfather's brother (which took a fair bit of record-digging to confirm). None of us had noticed her at Ancestry even though she'd been on the matchlist for months.
-
Not often linked but on ancestry i found some interesting matches when I used the surname match search function on ancestry it was an unusual me who a distant ancest+ had named as birth father of her child ,there were several trees with all cm matches who had this surname eventually found one with a full tree which traced back to same town and worked out the connection did correspond ,
On another branch while looking up my great great grandparents surnames +looking at trees I keep coming across another surname from earlier generation it could be a link but DNA matches will be small
-
Is a DNA match of say 7 cms 1 DNA segment of any value in ancestor matches ?
Even links of 5cM on GEDMATCH can be real. It's a question of how far back, and whether it goes back beyond when most people can practically trace a tree, and also, of whether it means much, when there might be hundreds of thousands if not millions of people who you share a 5 cM segment (or bigger) with. Given I have found 6cM link to people with common ancestors born in the late 18th century, but also 30cM links with people born in the late 17th century, I don't see why in theory a 5cM link could not also be from a common ancestor born in the early 19th century, but as far back as the 1300s.
-
I think the answer has got to be it depends ::)
I have identified one at 8cM, both our trees had the common ancestor with a fairly unusual name so obviously not a hard task! The relationship looks to be 4th cousins once removed.
I have other far higher matches though where things just aren’t lining up ???
-
I think the answer has got to be it depends ::)
I have identified one at 8cM, both our trees had the common ancestor with a fairly unusual name so obviously not a hard task! The relationship looks to be 4th cousins once removed.
I have other far higher matches though where things just aren’t lining up ???
See my comment above - I traced a group of 20-30 cM matches to a common ancestor born in the late 17th century. Most people do not have their tree traced back fully that far back. Even if they do maybe 2-5% of those ancestors will not be of the parent(s) they are meant to be from.
-
I’ve been able to place a new 6cM match in my tree this morning. She is a 5th cousin once removed.
-
Hello,
When is a science not a science? When it is biological! :)
GedMatch recommends over 7cM if you are using that criteria alone. The smaller you go the easier it is to get a match with anyone. I think I read elsewhere that 3cM gets that kind of result.
However, your percentage match may also matter. By trial and error initially, I realised that chasing links of 0.3% and less was a similar exercise. Yes, you can make connections but you are going way back and unless you have a really good, expansive tree to use, it is going to be a long job working out where it came from.
If you have an already well researched DNA and can place segments of DNA with known relatives then it is possible to go smaller (DNA painting comes in here)
One technique I use is to multiply the cM value by the number of SNPs, the bigger the score the more likely your going to find someone that touches your tree because both of you are likely to have known relatives to compare.
The thing for me is that the matches I want are the really small matches because I am back in the early 1800s and I have to find big matches to work their tree back to mine in some way.
Something I would recommend, as someone did already, is try to look for any match with given surnames off your tree. Obviously Smith might be a long shot.... However, also notice locations?
I have 12% Scandinavian genes as a surprise and one of the things I have been trying is collecting all the Scandinavian names, Johnson is the obvious name that is not in my tree. One thing that comes out of this is you will get many people from your 8000+ matches with the same surname - might be worth asking if a name recurs again and again. I have some notable links to people called Tucker with no idea where it comes from but it appears they have Scandinavian genes too!
When looking at possible matches I often use any combinations of these to make decisions about a letter of enquiry.
As the man said, "..it depends.." Make some fuzzy logic judgements on the items above and use your intuition too. It is isn't about science as such at this point?
One of the things lacking in DNA research is a how to guide on what to do with your results. Bits and pieces are given, but there is not an overall strategy as yet.
Hope this helps and please ask if I confused anyone?
-
Such a rush...
I forgot to mention segments, more segments means a closer match even if the segments added together are smaller than one, single segment (in my experience).
Lastly, if you have a small match, look for others that also have the same match - you need to download the data for all your matches from your results dupplier. Make them into a spreadsheet and sort by Chromosome, Start point and End point in that order. Scanning the list will give you possibles and the names of contacts?
Shay
-
I have a number of people identified as having a common ancestor with me on Ancestry who have 7cMs. My 5xggfather Thomas Broadley, born abt 1733, married twice. I'm descended from his first wife and Ancestry picked up 3 first cousins (to each other) in America from Thomas's second wife.
-
Also with the 7 cms and 1 segment thought maybe the 1 segment might be way too insignificant ? curious if the DNA Segments lower than say 5 segments are (hopeless)
Thank you Gadget Hurworth brigidmac meelystar melbaschmelba Avm28 shay123 Clayton bradley
-
Thanks for your explanations Shay I'm going to try out looking at some small matches linking to a larger match and look at names and locations. It will be a bit slap dash because I don't do spread sheets .so hope pseudo science works
-
Here's my pseudo science
I have a match of 38cm across 3 segments
A couple on her tree b 1875 Russia
Have 5 daughters
Several links in name matches to 4 of their married names
Matches are between 6-15cm but it looks like some are several generations younger .
So I'm building up a provisional tree to see if I can find a connection to this couples parents ...maybe find an unknown great grandmother
-
Hello,
The important thing to remember about "does size matter" is that below 7cm od course you can get a match, however, for most people researching the distance in generations is likely to be large and after 6 or seven very difficult to find the connection in terms of time and effort unless two people have very extensive trees?
Many people can not take their tree back very far eg Irish or American / Australian researchers the numbers of generations in a tree may be limited. 5 generations in my Irish tree takes me back to the beginning of national records.
Of course too, it is important to remember, that by chance, a segment may be passed along for longer than 6 or 7 generations.
So the gist of it is to say that for most people when they start out with DNA is not to chase the smaller stuff unless the mix of evidence suggest the time spent researching it.
I am fortunate that I can mostly spend as long as I want but even then, when people have only just started their tree, people do not reply, people have only one particular interest, people have a massive tree but do not want to divulge anything of it, it can still be difficult to find the time.
One last example and sorry for the personal example. I have two strong Scandanavian DNA links. My sister has our English line back to 1600s and we have connected with a know relative who has a 36% Scandi DNA connection and it is taking the three of us hours and hours of research over several weeks now and we still haven't unlocked it.
I know again that to find the clues to my own tree in Ireland I am working with small DNA connections but I have had to massively increase my tree and make new trees to track the connections between me and others. In fact it is becoming a one name study.
All DNA matches are potentially important but the question of size really related tot the amount of effort needed with small matches. "Triangulation" can help as brigidmac has explained.
Good luck!