Wednesday, 20 September 2017

Plea for MyHeritage DNA

Oh I do so wish MyHeritage would hasten along their promised Chromosome Browser so that where a match actually matches can be easily seen without a plea for them to upload to GEDmatch - although the latter upload is highly recommended regardless *.

* bewitched bothered and bewildered by GEDMatch?
Check out Jim Bartlett's latest post on his segmentology blog: Getting started with GEDMatch

My second wish is that such a tool would also differentiate between
- the components of the match that are real, from comparing apples with apples, and
- those bits that are imputed by MyHeritage in order to bring the set of SNPs being compared up to the full set
which latter comparison is apples with bananas, the last word being chosen deliberately.

My assumption is that this latter imputation is responsible for the example below (logged with MyHeritage for an explanation, and the two pleas above.)

An excited match contacted me about one of my kits saying "I'm a 1st cousin 2*removed can I see your tree please" adding later that "the connection should be easy to find".

Leaving aside that the tree was connected and visible, and that the match is actually listed under the heading MyHeritage labels as:
"DNA Matches listed below are lower quality matches that should be viewed with skepticism"
what MyHeritage reported was 

ie a total of 31.8cMs over 3 segments, largest segment 15.6cM

What Gedmatch reported at the default settings for the two ancestry kits, both presumed to be recent, ie post their chip change May/Jun 2016

Comparing Kit one and Kit two
Minimum threshold size to be included in total = 500 SNPs
Mismatch-bunching Limit = 250 SNPs
Minimum segment cM to be included in total = 7.0 cM

Largest segment = 0.0 cM
Total of segments > 7 cM = 0.0 cM
(2228) No shared DNA segments found

441115 SNPs used for this comparison.

Lowering the minimum segment cM to 5cM showed two small segments:
Chr Start Location End Location Centimorgans (cM) SNPs
1 120,064,541 151,437,807 5.5 684
9 127,173,028 131,032,682 5.1 524
Largest segment = 5.5 cM
Total of segments > 4 cM = 10.6 cM

We cannot yet find, and do not expect to, this match on Ancestry.