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STR marker mutations

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  • STR marker mutations

    We have now had two males of our family tested - my son and his father's 4th cousin. My son was tested for 67 markers and his cousin for 37. I have ordered upgrades for both. On 37 markers there are 4 differences between my son and his cousin, both with paper trails of male line ancestry going back to a shared ancestor in Latvia (Courland) in the late 1700s. We have records of brothers that my son and his cousin descend from from the early 1800s. The family emigrated to Argentina from Ukraine and has maintained knowledge of their cousinhood, as well as sharing a surname.

    Knowing that these two are descended from the same man and seeing a distance of 4 at 37 markers, I realized that my son may be more closely related to the others that he has Y-DNA matches than I originally thought. So I started looking at the markers where my son differs and they are DYS385, DYS389ii, DYS458, and CDY (? DYS 724). Three of the four are cited in numerous articles as markers that have a faster mutation rate. His cousin has the value that most of the others in the Y-DNA matches group has in 2/4 instances.

    I'm sure that there is discussion of this subject. What I'm hoping is to use this observation to assist me in figuring out how distant my son and his cousin are from the other matches (distance 4 - 7 out of 67 or 2 out of 37). Does this make sense?

  • #2
    Mutations happen at any time, and can happen in multiple instances with in 1 transmission event.

    All figures are based on the average mutation rate of STR markers.

    Based on my own experience of testing my Father and his paternal 1st Cousin, I have learned the key is to test multiple known lines to help rule out line that have the higher then average mutation rate.

    My father is a prime example of higher then average mutation rates. My Father and his 1st Cousin have a GD of 4 at 67 markers (GD of 1 @12 and GD of 4@37)
    Our line also has a unique marker value for 1 STR marker which seperates us from all other surname matches. This unique marker happened in their Grandfather or before (1850).

    My father and his brother are also a GD of 1 at the 37 marker level (only tested my Uncle to 37) and my Uncle is a GD of 3 to 1st Cousin @37.

    Marker Differences
    My Father is 2 Steps from Surname matches
    My Uncle is 1 Step
    Their cousin is identical to surname matches
    ** This indicates either my Grandfather had a 2 Step mutation and passed it on to my Father and it back mutated when passed on to my Uncle OR My Grandfather had a 1 step mutation and it mutated another Step in my Father.

    My father and his brother are 1 step from Surname matches
    Their cousin is identical to Surname matches
    **Indicates my Grandfather had a 1 Step mutation and passed it on to both sons.

    50/50 on whether My Father and his brother(brothers share same value) or their Cousin is 1 Step off Surname matches. Half Surname matches have my father and his brothers values, while the other half has their cousins value.
    **Indicates either my Grandfather or his Brother(my father's Uncle) had a 1 Step mutation.

    Both My Father, his brother and their 1st Cousin share the same 1 Step difference to Surname matches
    ** Indicates my Father's Grandfather or prior had a 1 step mutation.

    They key is to try and triangulated when these mutations took place. This will help determine the Generation range of matches.

    Currently the best markers are your son's 4th Cousin's for going the furthest back in time as it looks like he may fall into the average or below average mutation rate. Lines with lower then average also cause GD's and TiP Calculations to be off.

    It is my opinion that Triangulation, testing cousins (1st, 2nd, 3rd, ect), is the best way at determining a TMRA to matches to determine when any recent mutations have happened. Although this is not always an option.
    Last edited by prairielad; 13 November 2013, 03:02 PM.


    • #3
      Thank you for the very helpful answer and examples. I intend to get my brother-in-law tested if he'll agree and I know that one of the male cousins in Israel is planning to test as well. Luckily for us, there are a lot of male descendants. Four brothers emigrated from Latvia to Southern Ukraine but the descendants of only two of those brothers are represented in a large family in Argentina with a lot of male direct line descendants.

      What we don't have are any of the oldest generation alive, i don't believe. They seem to not have been long lived.