World Families Forums - What determines a "match"?

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Author Topic: What determines a "match"?  (Read 2022 times)
Marilyn Teaff Barton
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« on: April 02, 2007, 03:40:43 PM »

You ordered the test.  You swabbed your cheek.  You sent the kit back and waited.  Now your results are back.  But what does it mean?  How do I know if I "matched" someone, and what does it mean if I did?


In the simplest case, analyzing results can be a review of the number at each marker to confirm a perfect match (say  25/25).  However, in most cases, there will some matches and some mismatches.  Results are evaluated by counting the number of exact matches and the number of mismatches.  (If the mismatches are one number apart, they are considered a “one step” mutation.  If they are two numbers away, they are considered a “two step” mutation, etc.  Typically, a two step mutation is counted as two mismatches.  In these cases, contact the testing firm for guidance.)

Most researchers want to know if they are "related" to another person or family.  Here are some guidelines to help you understand your results when comparing them to other results:

For those who tested at 12 markers:

Matches of less than 9/12
– the two participants do not share a common ancestor*

Matches of 9/12 - there is a tiny chance  that the participants share a common ancestor.  You'll need to test at 37 markers to find a true shared genetic match that starts with such a low match.  (The author has not yet seen a 9/12 become an accepted genetic match - but has heard of one case)

Matches of 10/12 [/b] – there is a small chance that the participants share a common ancestor.  Increase to 25 markers and re-evaluate

Matches of 11/12 and 12/12 – there is an improved chance that the participants share a common ancestor.  Increase to 25 markers and re-evaluate

CAUTION: a 12/12 match - even with the same surname - can be a random match.  If a solid paper trail connects the 12/12 match, you can be reasonably certain of shared ancestry, but without the connecting paper trail - you can only be sure by upgrading to at least 25 markers

For those who tested at 25 markers:

Matches of less than 21/25 – the two participants do not share a common ancestor*

Matches of  21/25 & 22/25  – there is a small chance that the participants share a common ancestor.  Consider all of the traditional genealogy insights and try to obtain more participants to represent the affected families. Upgrade to 37 markers

Matches of  23/25, 24/25 & 25/25  – there is a high probability that participants who share a surname share a common ancestor.  If there is no shared paper trail, a comparison at 37 or 67 markers can be useful

You may also refer to the chart prepared by Family Tree DNA:  Click Here

For those who tested at 37 markers:

Matches of less than 31/37 – the two participants do not share a common ancestor*

Matches of 31/37 and 32/37 - the two participants have a small possibility that may share a common ancestor from the early days of surnames.  This is an area with little clear insight.  An upgrade to 67 markers is encouraged

Matches of 33/37 - some researchers consider this to be a match and some don't.  If there is a shared common ancestor - it will be more than a few 100s of years ago.  Upgrade to 67 markers for additional clarity

Matches of 34/37, 35/37, 36/37 & 37/37 - the participants share a recent common ancestor

You may also refer to the chart prepared by Family Tree DNA:  Click Here

For those who tested at 67 markers:

Matches of less than 60/67 – the two participants probably do not share a common ancestor*.  This is still being studied - but unless your match is nearly 60/67 and you have some reason to believe there is a shared ancestor since the advent of surnames - you should consider your near miss as "no match"

Matches of 60/67 and 61/67  - the two participants may share a common ancestor from the early days of surnames.  This is still being studied

Matches of 62/67 and better - researchers consider these to be a match - indicating a shared common ancestor

You may also refer to the chart prepared by Family Tree DNA:  Click Here

*We mean a common direct paternal ancestor within the historical period of surnames."
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