Announcement

Collapse
No announcement yet.

Tip Question?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Tip Question?

    A bit of a new be here, but on a 67 marker test does it make sense that a 67/65 match would have a higher probability then a 67/66 match of having a common ancestor in 4 generations? We have two 67/65 matches to my brother and their probabilities in the tip report jumped dramatically with the new changes. I can't comment on the 67/66 test because it was private until just very recently, but it seems strange to me that this is the case. The 67/66 match is at 70.79% and the two 67/65 markers are at 71.27%. They had been at something like 43% before the upgrade. I thought a 30% jump was a bit dramatic. The mismatches occurred in the first 37 markers.

    Any words of wisdom and knowledge would be most appreciated.

    Jim

  • #2
    The difference in TIP is likely based on the Y-STR's that are different in each case.

    There are "fast" and "slow" Y-STR's - Y-STR's known to be changeable (add/drop a repeat) and Y-STR's known to be resistant to change.

    In that case, the 65/67 TIP involves two of the "faster" Y-STR's and the 66/67 TIP involves one of the "slower" Y-STR's.

    http://www.familytreedna.com/faq-tip.aspx
    Last edited by tomcat; 28 December 2012, 10:48 AM.

    Comment


    • #3
      Thank you very much and the FAQ was helpful, but raises a question. My father was switched at birth. We all thought we descended from Irish Catholics, but a few months ago discovered that my father was Ashkenazi Jewish. So we are trying to find his family. What I noticed in the FAQ was that surname plays a role in the TIP calculations. In my brother's sample we have provided no surname. I believe that the two 67/65 matches also have no surname provided, but the 67/66 match does. Any idea on how this might affect the predictions and can you add and delete surnames for testing. The 67/66 match has an extensive family tree which closely matches my fathers know birth date and location.

      Thank you so much,

      Jim

      Comment


      • #4
        I would think that shared surnames, or close variants, could figure in TiP as the parallel of patronymic and Y descent is an original rationale for Y testing.

        I agree that factor should either be disabled or discounted in instances where there is a disjunction.

        Absent joint participation in a project, or sharing results by other means, there doesn't seem to be any way to compare STR profiles to determine if markers or surnames are responsible for the divergent TiP's.
        Last edited by tomcat; 28 December 2012, 12:46 PM.

        Comment

        Working...
        X