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Old 23rd December 2017, 07:20 AM
chr chr is offline
FTDNA Customer
Join Date: Nov 2017
Posts: 18
hello GST, thanks for your help with that. What you've written is the most detailed I found on how GD is calculated. I just have a hard time understanding this, I tried this a few times but needed a break because I was frustrated. It seems like the calculation you mentioned does not work for the match that I'm looking at. Probably I didn't understand you.

Originally Posted by GST View Post
H10e includes the defining mutation T16093C
A: T16093C (H10e reference)
B: CT16093T! (person in H10e with reversion at 16093)
C: T16093Y

Person C is 2 step distance from person A.
Person C is 1 step distance from person B.
This looks similar to my example above, except I get GD1 instead of GD2 like in your quoted example.

H86 implies C195T (from way back group "'L2'3'4'6'"), so:

A: C195T (my match; just for this SNP: GD0 to H86 reference, GD1 to RSRS)
C: C195Y (me; just for this SNP: GD1 to H86 reference, GD1 to RSRS)

If I understand your examples right, this would mean for the calculated GD between us:
(1) each of us has like a "GD1" to RSRS for this position
(2) we also have a different value from each other in this position, so:
(3) our "GDs" to RSRS in this position are added, resulting in overall GD2 between us. Did I understand you right in that?

Unfortunately this calculation does not work for me, as I received GD1 (and not GD2!) for this match. Every other position that I can see (HVR1, HVR2) being the same apart from position 195. It barely makes sense to receive GD1 for this match, but GD2 would make even less sense.

I'm a bit disappointed that there's no info by FTDNA what concerns the actual rules of GD calculation, maybe these unknown rules also changed over time...?

Meanwhile, since I also didn't get info from FTDNA about the actual degree of my heteroplasmy (for Y: the ratio between DNA with C and DNA with T Allele) other than there's a general 20% threshold for heteroplasmy reporting, I re-tested HVR1+2 at YSEQ, and received the results last night. I'll do a post on that in the next days.

Happy Christmas everyone!
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