Author Topic: MyHeritage Chromosome Browser.  (Read 340 times)

Offline aghadowey

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Re: MyHeritage Chromosome Browser.
« Reply #9 on: Wednesday 06 October 21 13:24 BST (UK) »
Very interesting post on other forum but can't say that I'm surprised.
Away sorting out DNA matches... I may be gone for some time many years!

Offline Althea7

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Re: MyHeritage Chromosome Browser.
« Reply #10 on: Wednesday 06 October 21 13:27 BST (UK) »
Thanks for your replies and links.  Yes very interesting suggestions about what could be happening.

I also wonder if it is significant that all my matches' segments include the centromere on Chromosome 1, which is 1215 to 1245.  They typically run from about 1100 to 1400 or 1500.

It could just be that they are IBS rather than IBD (Identical By Descent) as Melba_Schmelba pointed out.  Or as people on the links are suggesting, something else more complicated.

I did notice that one of these matches is an American lady in New York who has a lot of Swedish ancestors in her family tree, which would back up the IBS explanation.

I did upload my Ancestry DNA test to MyHeritage.  I have noticed that MyHeritage seems to give higher cM numbers to matches than Ancestry.

Offline melba_schmelba

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Re: MyHeritage Chromosome Browser.
« Reply #11 on: Wednesday 06 October 21 14:29 BST (UK) »
Thanks for your replies and links.  Yes very interesting suggestions about what could be happening.

I also wonder if it is significant that all my matches' segments include the centromere on Chromosome 1, which is 1215 to 1245.  They typically run from about 1100 to 1400 or 1500.

It could just be that they are IBS rather than IBD (Identical By Descent) as Melba_Schmelba pointed out.  Or as people on the links are suggesting, something else more complicated.

I did notice that one of these matches is an American lady in New York who has a lot of Swedish ancestors in her family tree, which would back up the IBS explanation.

I did upload my Ancestry DNA test to MyHeritage.  I have noticed that MyHeritage seems to give higher cM numbers to matches than Ancestry.
The mysterious Swedish/Norwegian matches is definitely a 'thing' with MyHeritage, discussed quite often here and on other forums. It could either be IBS or simply false matches - as the other person did find up to a 1/3 of matches under 17.6cM segments can be falsely imputed by the matching algorithm. It may be that with a MyHeritage tested person matching to another MyHeritage tested person, they are more likely to be real matches, even at lower segments. The problem is, as far as I know there is no way to know if a match is an upload or a MH test, or what company or chip the upload is from. It is probable that a similar proportion of the smaller segment matches on GEDMATCH are also false, especially if matching to a different company/chip, but at least on GEDMATCH you can see where the person tested - the overlap can also give you an idea.