Minimum

[Frederator]

I'll have to re-read this to be sure I really understand.

But my sense is that it is introducing some information that is new to me--suggesting that the testing process itself clearly distinguishes between the A & B chromosome copies. If true, I had long suspected it, but never knew that for an actual fact. Probably I should have known this earlier but I did not.

Also if that is true, then, once I have a 2nd sibling of my own tested, I will theoretically already have enough information to phase my father's (at least nearly) 100% reconstructed kit into partial kits for both of my paternal grandparents.

My paternal grandmother's matches are genealogically and ethnically distinct from my paternal grandfather's because she was from eastern Europe and he was from western Europe. If I designate one genealogical match from each chromosome as representing A or B, by default the other chromosome must represent the contribution from the other grandparent.

These would only contain 1/2 the cM of an ordinary living donor, but it would still be interesting and useful.

Even if that is technically correct, is it something the interface of the Gedmatch reconstruction utility could even handle? Or does their format require full siblings?

[prairielad]

Originally Posted by Frederator

I'll have to re-read this to be sure I really understand.

But my sense is that it is introducing some information that is new to me--suggesting that the testing process itself clearly distinguishes between the A & B chromosome copies. If true, I had long suspected it, but never knew that for an actual fact. Probably I should have known this earlier but I did not.
........

In a sense, yes testing process can distinguish between parent A and parent B, but only in little segments, as DNA is broken down into little segments to be read by chip and then it is "pieced back together" using a "template" to give raw data (multiple strands of DNA used, not just one single chromosome). Thus it can not say with certainty which "segment" belong together to make each parent A and parent B single chromosome per pair. ( testing process a little more complicated then that....)

[Frederator]

Darn. Well, thanks at least for setting me straight.

[prairielad]

Here are my figures per chromosome using 3 and 4 siblings
Figures are based on tested positions (tested SNPs) inherited per chromosome.
Factors in 2 Values per position (maternal and paternal)

[Frederator]

Those are remarkably close to Jean's calculations.

[prairielad]

Originally Posted by Frederator

Thanks. This is a more thorough practical example than I could have hoped for.

But I'm not sure I understand some key points yet. How is it possible that you have phased your grandparents' kits into parent A and parent B if you haven't firmly established a kit/kits representing specific great grandparent(s) as a reference? I thought you needed a minimum of one parent (or a collection of close cousins from one side of the family) to phase a kit.

Sorry if those questions are phrased a little awkwardly. Hopefully you get my gist.

To expand on / clarify.

I have 1st Cousins of my parents tested to identify which DNA is maternal(mothers Parent A and Parent B) vs paternal (Fathers Parent A and Parent B) in each sibling per chromosome.

Each recreated parents DNA is "phased" per chromosome into their Parent A and Parent B single chromosomes, but Parent A on one chromosome maybe Parent B on next.

Can not build a maternal and paternal phased file of a Grandparent until I can identify which Parent is which of said Grandparent