Another newbie question...

[rachelleleclaire]

If you match say, 6 people on an identical block of DNA same start and end locations... is it fair to say there's a good chance the seven of you share a common ancestor? I know there are two strands in the DNA and overlapping segments may look like a match but can actually not be. But what are the chances with an exact segment?
I have an 8 cM segment which I match several people with some pretty varying Eastern European backgrounds that's intriguing me..

Oh and also, what does it mean if you have a small cM segment with a large SNP amount? Ie. A 1.06 cM segment with a 2300 SNP?

[adr]

If you match say, 6 people on an identical block of DNA same start and end locations... is it fair to say there's a good chance the seven of you share a common ancestor? I know there are two strands in the DNA and overlapping segments may look like a match but can actually not be. But what are the chances with an exact segment?
I have an 8 cM segment which I match several people with some pretty varying Eastern European backgrounds that's intriguing me..

Oh and also, what does it mean if you have a small cM segment with a large SNP amount? Ie. A 1.06 cM segment with a 2300 SNP?

I can't help you but i'm also wondering about the second question, i've tried to get the information through internet without any luck.

I have another question about a match, 45cM, 30 (longuest B) would you contact this match ?

Thanks

[Armando]

I can't help you but i'm also wondering about the second question, i've tried to get the information through internet without any luck.

I have another question about a match, 45cM, 30 (longuest B) would you contact this match ?

Thanks

Under 1 cM you have a extremely low chance of having a common ancestor in a genealogical time frame. Blocks between 1 cM and 4.9 cM shouldn't even looked at.

Over 12 cM you have a good chance of having a common ancestor in 12-15 generations but there are still instances of false matches at that length.

At 45 cM you have an extremely good chance of being related within 5 generations.

No matter what you always want to get your parents tested, if possible, and their parents tested, if possible, to see if the matches hold up. If the parents aren't available get as many other close relatives to test as possible in order to triangulate.

Using Genome Mate makes triangulation easy http://genomemate.org/ as does Gedmatch if enough people have uploaded their files there.

http://www.thegeneticgenealogist.com/2014/12/02/small-matching-segments-friend-foe/

http://dna-explained.com/2014/11/30/chromosome-browser-war/

http://www.isogg.org/wiki/Autosomal_DNA_statistics

http://www.jogg.info/72/files/Turner.htm