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Old 9th July 2018, 09:13 PM
DRNewcomb DRNewcomb is offline
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Question Could a STR no-call throw off results?

Here's the situation. I recently got the results of my Y-67 test. It had been delayed to be rerun for QA reasons. Right now I'm seeing 14 matches a Y-12, none at Y-25 & 37 and two at Y-67. The problem is that the Y-67 matches have a genetic distance of 6 & 7. They appear to be 6th to 8th cousins.

I noticed that the DYS448 STR on my test was reported as a null. This STR is part of the Y-25 tests. The other matches seem to have a DYS448 value of 19.

My question is if this could be a no-call that is throwing off my results, giving me no matches at the Y-25 & 37 levels and increasing the genetic distance on the Y-67 matches?
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Old 10th July 2018, 07:06 AM
Jim Barrett Jim Barrett is offline
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Quote:
Originally Posted by DRNewcomb View Post
I noticed that the DYS448 STR on my test was reported as a null. This STR is part of the Y-25 tests. The other matches seem to have a DYS448 value of 19.

My question is if this could be a no-call that is throwing off my results, giving me no matches at the Y-25 & 37 levels and increasing the genetic distance on the Y-67 matches?
YES! In fact I'd expect your two Y-67 matches have a null at DYS448 also.
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Old 10th July 2018, 09:27 AM
DRNewcomb DRNewcomb is offline
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Originally Posted by Jim Barrett View Post
YES! In fact I'd expect your two Y-67 matches have a null at DYS448 also.
Actually, I believe that they have a 19, like just about every other Newcomb male. At least one of them is a member of the Newsome project and I noticed that I'm the only member with a null DYS448. I believe that this is the reason I match 14 people at Y-12 but none at Y-25 or 37. The DYS448 STR is in the 2nd (14-25) STR panel. If it throws the GD out beyond the cutoff, the matches disappear.
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Old 10th July 2018, 10:21 AM
TwiddlingThumbs TwiddlingThumbs is offline
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Back in 2016, FTDNA changed their method of calculating genetic distance with respect to null values, so that, with respect to certain STR's, a null value was treated a single mutation. However, in August 2017 someone posted the following response by FTDNA to an inquiry about DYS448 null values:

"Our team has confirmed that while some markers, mostly multi copy markers, will have deletions counted as single genetic event. Unfortunately DYS448 is not among these markers at this time."

It seems pretty clear that ALL null values would be better treated as a single mutation. However, apparently, FTDNA has not yet corrected their program to do so.

The result of not treating a DYS448 null value as a single mutation is that your DYS448 null value is, by itself, resulting in a genetic distance of 19 from the other Newcomb males, which is way beyond the cutoff for a match.

Last edited by TwiddlingThumbs; 10th July 2018 at 10:25 AM.
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Old 10th July 2018, 04:43 PM
DRNewcomb DRNewcomb is offline
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Thanks all for the replies. I've been taking a crash course on deleted Y-chromosome markers. Did you know that there's a project just for Null DYS448s? Right now I'm debating if I want to approach one of my brothers or my remaining male Newcomb first-cousin about taking a Y-chromosome test. It would be interesting to know who dropped the proverbial genetic ball. For all I know it could be me.

I'm also trying to contact the Newcombs that I do match on the Y-chromosome and who don't have trees posted to see if we can determine where we connect. It could help bracket the range places where the deletion might have occurred.
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