Tuesday, April 11, 2017

Roberta Estes shares... Please read DNA Information

New post on DNAeXplained - Genetic Genealogy



Somehow, I missed the announcement that Family Tree DNA now accepts uploads from MyHeritage. Other people may have missed a few announcements too, or don't understand the options, so I’ve created a quick and easy reference that shows which testing vendors' files can be uploaded to which other vendors.
Why Transfer?
Just so that everyone is on the same page, if you test your autosomal DNA at one vendor, Vendor A, some other vendors allow you to download your raw data file from Vendor A and transfer your results to their company, Vendor B.  The transfer to Vendor B is either free or lower cost than testing from scratch.  One site, GedMatch, is not a testing vendor, but is a contribution/subscription comparison site.
Vendor B then processes your DNA file that you imported from Vendor A, and your results are then included in the database of Vendor B, which means that you can obtain your matches to other people in Vendor B's data base who tested there originally and others who have also transferred.  You can also avail yourself of any other tools that Vendor B provides to their customers.  Tools vary widely between companies.  For example, Family Tree DNA, GedMatch and 23andMe provide chromosome browsers, while Ancestry does not.  All 3 major vendors (Family Tree DNA, Ancestry and 23andMe) have developed unique offerings (of varying quality) to help their customers understand the messages that their unique DNA carries.
Ok, Who Loves Whom?
The vendors in the left column are the vendors performing the autosomal DNA tests. The vendor row (plus GedMatch) across the top indicates who accepts upload transfers from whom, and which file versions. Please consider the notes below the chart.

·         Family Tree DNA accepts uploads from both other major vendors (Ancestry and 23andMe) but the versions that are compatible with the chip used by FTDNA will have more matches at Family Tree DNA. 23andMe V3, Ancestry V1 and MyHeritage results utilize the same chip and format as FTDNA. 23andMe V4 and Ancestry V2 utilize different formats utilizing only about half of the common locations. Family Tree DNA still allows free transfers and comparisons with other testers, but since there are only about half of the same DNA locations in common with the FTDNA chip, matches will be fewer. Additional functions can be unlocked for a one time $19 fee.
·         Neither Ancestry, 23andMe nor Genographic accept transfer data from any other vendors.
·         MyHeritage does accept transfers, although that option is not easy to find. I checked with a MyHeritage representative and they provided me with the following information:  "You can upload an autosomal DNA file from your profile page on MyHeritage. To access your profile page, login to your MyHeritage account, then click on your name which is displayed towards the top right corner of the screen. Click on "My profile". On the profile page you'll see a DNA tab, click on the tab and you'll see a link to upload a file."  MyHeritage has also indicated that they will be making ethnicity results available to individuals who transfer results into their system in May, 2017.
·         LivingDNA has just released an ethnicity product and does not have DNA matching capability to other testers.  They also do not provide a raw DNA download file for customers, but hope to provide that feature by mid-May. Without a download file, you cannot transfer your DNA to other companies for processing and inclusion in their data bases. Living DNA imputes DNA locations that they don’t test, but the initial download, when available, file will only include the DNA locations actually tested. According to LivingDNA, the Illumina GSA chip includes 680,000 autosomal markers. It’s unclear at this point how many of these locations overlaps with other chips.
·         WeGene’s website is in Chinese and they are not a significant player, but I did include them because GedMatch accepts their files. WeGene’s website indicates that they accept 23andme uploads, but I am unable to determine which version or versions. Given that their terms and conditions and privacy and security information are not in English, I would be extremely hesitant before engaging in business. I would not be comfortable in trusting on online translation for this type of document.SNPedia reports that WeGene has data quality issues.
·         GedMatch is not a testing vendor, so has no entry in the left column, but does provide tools and accepts all versions of files from each vendor that provides files, to date, with the exception of the Genographic Project.  GedMatch is free (contribution based) for many features, but does have more advanced functions available for a $10 monthly subscription.
·         The Genographic Project tested their participants at the Family Tree DNA lab until November 2016, when they moved to the Helix platform, which performs an exome test using a different chip.
Incompatible Files
Please be aware that vendors that accept different versions of other vendors files can only work with the tested locations that are in the files generated by the testing vendors unless they use a technique called imputation.
For example, Family Tree DNA tests about 700,000 locations which are on the same chip as MyHeritage, 23andMe V3 and Ancestry V1. In the later 23andMe V4 test, the earlier 23andMe V2 and the Ancestry V2 tests, only a portion of the same locations are tested.  The 23andMe V4 and Ancestry V2 chips only test about half of the file locations of the vendors who utilize the Illumina OmniExpress chip, but not the same locations as each other since both the Ancestry V2 and 23andMe V4 chips are custom. 23andMe and Ancestry both changed their chips from the OmniExpress version and replaced genealogically relevant locations with medically relevant locations, creating a custom chip.
I know this if confusing, so I’ve created the following chart for chip and test compatibility comparison.

You can easily see why the FTDNA, Ancestry V1, 23andMe V3 and MyHeritage tests are compatible with each other.  They all tested utilizing the same chip.  However, each vendor then applies their own unique matching and ethnicity algorithms to customer results, so your results will vary with each vendor, even when comparing ethnicity predictions or matching the same two individuals to each other.
Apples to Apples to Imputation
It’s difficult for vendors to compare apples to apples with non-compatible files.
I wrote about imputation in the article about MyHeritage, here. In a nutshell, imputation is a technique used to infer the DNA for locations a vendor doesn’t test (or doesn’t receive in a transfer file from another vendor) based on the location’s neighboring DNA and DNA that is “normally” passed together as a packet.
However, the imputed regions of DNA are not your DNA, and therefore don’t carry your mutations, if any.
I created the following diagram when writing the MyHeritage article to explain the concept of imputation when comparing multiple vendors' files showing locations tested, overlap and imputed regions. You can click to enlarge the graphic.

Family Tree DNA has chosen not to utilize imputation for transfer files and only compares the actual DNA locations tested and uploaded in vendor files, while MyHeritage has chosen to impute locations for incompatible files. Family Tree DNA produces fewer, but accurate matches for incompatible transfer files.  MyHeritage continues to have matching issues.
MyHeritage may be using imputation for all transfer files to equalize the files to a maximum location count for all vendor files. This is speculation on my part, but is speculation based on the differences in matches from known compatible file versions to known matches at the original vendor and then at MyHeritage.
compared matches to the same person at MyHeritage, GedMatch, Ancestry and Family Tree DNA. It appears that imputed matches do not consistently compare reliably. I’m not convinced imputation can ever work reliably for genetic genealogy, because we need our own DNA and mutations. Regardless, imputation is in its infancy today.
To date, two vendors are utilizing imputation. LivingDNA is using imputation with the GSA chip for ethnicity, and MyHeritage for DNA matching.
Summary
Your best results are going to be to test on the platform that the vendor offers, because the vendor’s match and ethnicity algorithms are optimized for their own file formats and DNA locations tested.
That means that if you are transferring an Ancestry V1 file, a 23andMe V3 file or a MyHeritage file, for example, to Family Tree DNA, your matches at Family Tree DNA will be the same as if you tested on the FTDNA platform.  You do not need to retest at Family Tree DNA.
However, if you are transferring an Ancestry V2 file or 23andMe V4 file, you will receive some matches, someplace between one quarter and half as compared to a test run on the vendor’s own chip. For people who can’t be tested again, that’s certainly better than nothing, and cross-chip matching generally picks up the strongest matches because they tend to match in multiple locations. For people who can retest, testing at Family Tree DNA would garner more matches and better ethnicity results for those with 23andMe V2 and V4 tests as well as Ancestry V2 tests.
For absolutely best results, swim in all of the major DNA testing pools, test as many relatives as possible, and test on the vendor's Native chip to obtain the most matches.  After all, without sharing and matching, there is no genetic genealogy!
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