GENEALOGY-DNA-L Archives

Archiver > GENEALOGY-DNA > 2002-07 > 1027097340


From: "John F. Chandler" <>
Subject: Re: [DNA] RFLP siblingship tests
Date: Fri, 19 Jul 2002 12:49 EDT
In-Reply-To: DNACousins@aol.com message <155.111d52b1.2a696b19@aol.com> of Fri, 19 Jul 2002 07:16:13 -0600


Ann wrote:
> Chris wrote that the lab report said "When
> compared to two siblings, there was a 99.98% probability of have the SAME
> mother AND father, with two others the result was 98.7% probability and with
> the last sister..again..about 56%." Do you suppose the lab was calculating
> probabilities one pair at a time, rather than for the whole group at once?

That would be my guess. I haven't worked out the math, but I think it
gets complicated very quickly as you start to consider more than two
putative siblings at once.

> Chris queried the lab on the missing band. Apparently he had only the 2.73
> band, and was therefore presumably homozygous (both the father and the mother
> had a 2.73 band). This is still consistent with full siblingship.

Ah, I see. I would have thought, though, that the assay could be
at least semi-quantitative -- ok, he had only the one band for 2.73,
but was it about twice as intense as a normal band?? If so, the
report should give the 2.73 number twice to avoid confusion. This
is exactly the sort of thing that the Y STR testing labs seem to
manage successfully with DYS385a,b and the like.

John Chandler

This thread: