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How close does a match have to be?

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  • How close does a match have to be?

    This is all new to me. My husband has a match that is -1 for HRV1. What does that mean if it's not exact but off by one HRV mutation? The HRV2 is exact. Does that mean the near match is not related or that they are?

  • #2
    Originally posted by birdy06
    This is all new to me. My husband has a match that is -1 for HRV1. What does that mean if it's not exact but off by one HRV mutation? The HRV2 is exact. Does that mean the near match is not related or that they are?
    Matches that close are almost certainly related, the only question is really about how recent the relationship is.

    A difference of one mutation on HVR1 + HVR2 combined (which is you husband's situation) indicates that the people you are comparing probably have a common ancestor more than ten generations ago (250 years) and possibly as much as 80 generations ago (2,000 years). The most likely estimate is about 20 generations ago (about 500 years).

    This is outside the genealogical range for many people, but it could point to a certain common geographic origin (country, clan, or tribe).

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    • #3
      An exact match at both HVR1 and HVR2 is said to have a 50% chance of being related within the past 28 generations (~700 years). Anything less than an exact match will be even further beyond that timeframe. So for genealogical purposes, I wouldn't consider anyone who has a different mutation than you do at either HVR1 or HVR2 or both.

      See FTDNA's mtDNA FAQ for more information:
      http://www.familytreedna.com/mtDNA_tutorial.html

      The mtDNA Full Sequence test gives the best resolution for genealogy. The downside is that it has traditionally been very pricey, so comparatively few people have taken the full sequence test. On the upside, the cost was significantly reduced several months ago, so more people are now beginning to upgrade to the full sequence test.
      Last edited by efgen; 24 January 2007, 01:24 PM.

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      • #4
        Originally posted by vineviz
        A difference of one mutation on HVR1 + HVR2 combined (which is you husband's situation) indicates that the people you are comparing probably have a common ancestor more than ten generations ago (250 years) and possibly as much as 80 generations ago (2,000 years). The most likely estimate is about 20 generations ago (about 500 years).
        Where did you get 20 generations from?

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        • #5
          Originally posted by efgen
          Where did you get 20 generations from?
          I used Doug McDonald's TMRCA calculator (http://dna-project.clan-donald-usa.org/tmrca.htm), with the following inputs.

          Number of markers = 1050
          Number of markers that match = 1049
          Mutation rate = .0025

          The maximum probability occurs at 38 transmission events (i.e. 19 generations).

          The cumulative probability is still low at that age, as you pointed out. The cumulative probability doesn't reach 50 percent until 32 generations (800 years).

          Family Tree DNA likely used a different mutation rate assumption in their calculation than I did.

          Either way, the odds of a common ancestor within genealogical time frames (e.g. 150 years) are pretty low.

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          • #6
            Thanks for taking the time to post this. Makes sense to me. So it still is interesting to know they were from the same area at one time, even if it is hundreds of years ago!

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