Family Finder versus DNA Relatives

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There are two autosomal DNA tests currently on the market which enable the customer to make connections with close cousins by comparing matching autosomal DNA SNPs. 23andMe's DNA Relatives service (formerly known as Relative Finder) is a tool provided as part of its personal genomics service. Relative Finder was launched in a public beta-test on November 19, 2009.[1] Family Tree DNA sell their Family Finder test as a standalone product. The Family Finder test provides genealogical matches but the company does not offer a health analysis. Family Finder was launched in a phased release beginning in February 2010. This page provides a comparison between the two tests.

Overview

DNA Relatives (formerly Relative Finder)

(Specimens analyzed by 23andMe through mid-November 2010 were processed with version 2 ("v2") of their assay (even if results are viewed or downloaded after that date). Specimens analyzed after mid-November 2010 use version 3 ("v3") of their assay. Many specifications for version 3 have not yet been released; many of the figures below will need to be revised when data is available. Further, the number of SNPs reported is approximate; these will change slightly as the company re-evaluates the accuracy of specific SNP calls on an ongoing basis. For all data pertaining to 23andMe below, assume that the data refers to v2 unless it is specified otherwise.)

  • Uses a customized Illumina OmniExpress Plus Genotyping BeadChip for v3 (a customized Illumina 550K for v2
  • Tests 578,320 autosomal DNA SNPs for v2
  • Tests 3100 Y chromosome SNPs for v3 (1900 for v2)
  • Tests 14,000 X chromosome SNPs for v2
  • Tests 2700 mitochondrial DNA SNPs for V3 (2000 for v2)
  • Ancestry Painting attempts to predict from which of three regions of the world your ancestors came (Europe, Africa, Asia)
  • Ancestry Finder attempts to predict from which countries of the world your ancestors came
  • Native American Ancestry Finder attempts to predict whether a person has NA Ancestry in the last five generations
  • Global Similarity illustrates to which countries or ethnic groups one is most closely related
  • Family Inheritance: Advanced Lab graphically illustrates the matching DNA segments between customers
  • Gives information based on scientific studies about medical conditions to which one might be predisposed
  • Gives information in regard to Mendelian disease carrier status
  • Gives information based on scientific studies about individual traits
  • Allows comparisons to other people using Relative Finder
  • Customers can download their raw data
  • Does not allow upload of raw data from other companies

Family Finder

(This section is outdated. Family Finder initially used an Affymetrix chip but converted to an Illumina assay on 1 February 2011.[2] The data below have not yet been updated.)

  • Uses Affymetrix’ Axiom CEU SNP chip
  • Tests 563,800 autosomal DNA SNPs
  • Tests no Y chromosome SNPs
  • Tests 15,789 X chromosome SNPs
  • X chromosome browser in beta-testing
  • Tests no mitochondrial DNA SNPs
  • Population Finder provides an admixture analysis based on comparisons with reference populations worldwide
  • Gives no information about medical conditions one might be predisposed to since the 3,296 medically relevant SNPs have been removed
  • Allows comparisons to other people similar to DNA Relatives
  • Customers can download their raw data

Autosomal SNPs in common

This information is based on a comparison between the 23andMe version 2 chip and the FTDNA Affymetrix chip and is therefore outdated.

  • SNPs in common: 148,045
  • SNPs unique to 23andMe: 430,275
  • SNPs unique to Family Finder: 415,755
  • Conclusion: little overlap between the two tests (This conclusion is outdated.)

X chromosome SNPs in common

This information is based on a comparison between the 23andMe version 2 chip and the FTDNA Affymetrix chip and is therefore outdated.

  • X SNPs in common: 2283
  • X SNPs unique to 23andMe: 11,593
  • X SNPs unique to Family Finder: 13,506
  • Conclusion: little overlap between the two tests (This conclusion is outdated.)

Thresholds for relationship matches

Because these tests report scattered SNPs and not the complete DNA sequence, and because the results are not phased (each SNP reports two nucleotides, but we do not know which copy of the chromosome each nucleotide is on), a short segment of DNA may appear to be identical in two individuals when in actuality it is not. Therefore we must resort to the use of statistics to determine whether two matching segments are PROBABLY in fact half- or fully identical. The following are thresholds set by each company to indicate that two matching individuals very likely inherited their segments from a common ancestor.

DNA Relatives

(Thresholds [3] for the 23andMe assay reported below pertain to v2. If thresholds have changed for v3, the changes have not been publicized.) For DNA Relatives, but not for Ancestry Finder, at least one segment must equal or exceed 7 centimorgans (cMs).

For half-Identical by descent (IBD) segments]], the thresholds are:

  • Autosomal: 700 SNPs, 5 cM
  • X (male vs male): 200 SNPs, 1 cM
  • X (male vs female): 600 SNPs, 6 cM
  • X (female vs female): 1200 SNPs, 6 cM

The maximum amount of error tolerated in a half-IBD segment would be roughly 1 opposite homozygote per 300 SNPs; furthermore, each such opposite homozygote in a half-IBD segment must be separated by roughly 300 SNPs (i.e., the length of a sub-segment).

For full-IBD segments, the thresholds are:

  • Autosomal and X: 500 SNPs, 5 cM.

The criteria roughly correspond to allowing an error rate of 1%.

Family Finder

Total shared cMs are used to determine up to and including 2nd cousin; for 3rd cousin and more distant they use largest cMs plus a formula to determine these: 1st longest block, 2nd longest block above 5 cMs, then total of all cMs, 500 SNPs and above.

It appears from anecdotal reports that Family Finder does not report matches below about 7.5 cM, so this is the de facto autosomal threshold. Family finder does not currently report matches on the X chromosome at all, although it is said this will be offered in the future.

Each company has made reasonable choices for thresholds. Both are trying to strive for that "middle ground" between missing true matches where people share a common ancestor within the past 300–400 years, and including too many people as matches who don't share a common ancestor within the past 500 or so years.

Databases

In October 2009, prior to the launch of the 23andMe Relative Finder service, the company announced that it had '30,000 "active" genomes in its database.[4] By July 2010 the database had grown to 50,000 customers.[5] As of June 2011 23andMe had over 100,000 customers in their database.[6] The company does not provide a breakdown of customers by country. Anecdotal evidence suggests that the vast majority of their customers, and perhaps in excess of 90%, are in the United States.

Family Tree DNA's Family Finder test was launched in February 2010. Although Family Tree DNA publicise figures for the size of their Y-DNA and mtDNA databases[7] they have not publicly disclosed the size of their Family Finder database. However, a subscriber to the Rootsweb Autosomal DNA mailing list reported that Bennett Greenspan, the CEO of FTDNA, had announced at a Jewish genealogy meeting in September 2011 that the Family Finder database had passed the 20,000 milestone.[8] Family Tree DNA has a much more international database than 23andMe, largely thanks to their involvement with the Genographic Project. The company does not provide a breakdown of customers by country. It is estimated that over 30% of their customers live outside the US, with the United Kingdom being the second largest population in the database after the US.

Match menu

Because DNA Relatives incorporates both Ancestral and Health tests, their match menu does not give the names of your matches. You are given the Predicted Relationship, Relationship Range, whether the match is male or female, percentage of DNA shared and number of shared segments. From that menu you have a Make Contact button to send a message to your match to see if they wish to correspond further. All contact goes through an internal mailing system within 23andMe.

Family Finder is an ancestral test only, so when you access the match menu you are able to see the names of your matches, as well as the Suggested Relationship, Relationship Range, Shared cM, Longest Block and Ancestral Surnames. Under your matches name you have a notes option where you can input notes regarding this match, as well as an email option where you can contact your match. This contact goes through your computer email program apart from FTDNA.

Match responsiveness

The responsiveness of matches at 23andMe is not very high. Many who order the tests have ordered for the health side, and are not interested in genealogy. Though 23andMe has a larger database at this time, many have not researched their family and do not respond when you contact them. Even if they respond, they usually have little information regarding their family trees. The response rate is higher for Family Finder as most of the initial customers were Group Administrators running genetic genealogy projects. The Family Finder test is for ancestral research only and attracts a different audience than DNA Relatives. Because of this, it is expected that Family Finder will have a better response rate in general and the contacts will be more fruitful.

Customer service

Family Tree DNA is known for its excellent customer service and response. Questions are answered in a timely manner either by email or phone call. Currently, 23andMe is not very responsive to its customers. It is not unusual to wait several days for a response to a question either by email or by phone call.

References

  1. Introducing Relative Finder: the newest feature from 23andMe 23andMe Spittoon blog, 19 November 2009.
  2. What was the Family Finder Affymetrix to Illumina Chip conversion? FTDNA FAQs.
  3. X Marks the Spot -thread with threshold details. (Access is restricted to account holders.)
  4. Brian Dolan. 23andMe has 30,000 "active" genomes, launching "Relative Finder" soon TEDMED, 28 October 2009.
  5. 23andMe and a new paradigm for research. 23andMe Spittoon blog, 22 June 2010.
  6. 23andMe 2011 State of the Database Address. 23andMe Spittoon blog, 15 June 2011.
  7. About the FTDNA database, Family Tree DNA website
  8. Herb McDaniel. Posting on the Autosomal DNA mailing list, 4 October 2011.

Further reading

See also