Success with brother a GD of 1 at 25?

[Zaru]

I had my brother tested to prove paternity and we are a gd of 1 (dys 458=16 for him and 17 for myself). I was certain that we would match exactly, but for those of you who are familiar with my DNA signature, he is only my second match in the database postings. I actually thought that we would differ at dys 449 = 32 but we didn't.

Can I take anything away from this, or, should I go all the way with 63 markers? At what point should I raise my eyebrows?

Cheers,

Rosario

Y Search= 9epze

[cacio]

I'd say the Y chromosome has given all the information it can give on the matter, and it's a match.

For legal purposes, of course, that would not be conclusive, because itsimply says that it's from the same paternal origin (could be uncles etc.) - one would need autosomal data as well, not just the Y.

cacio

[Zaru]

I'd say the Y chromosome has given all the information it can give on the matter, and it's a match.

For legal purposes, of course, that would not be conclusive, because itsimply says that it's from the same paternal origin (could be uncles etc.) - one would need autosomal data as well, not just the Y.

cacio

The test was only a 25 marker and not a 67. I am wondering about possibilities beyond 25. Is it possible that since we do not match exactly, that there could be more mismatches beyond 25?

[cacio]

This is certainly possible, in general. When one compares two random people with no suspected shared ancestry, then it is worthwhile to go to 67 - the point being that there could be many near matches at 25 who are only very distantly related (in the sense of hundreds and hundreds of years), and the 67 test helps in estimating the time to most recent common ancestor.

But your case is different, you are starting from a person whom you know or suspect is your brother. What is the likelihood that this person is not closely related to you and yet shares your same paternal lineages 24/25? That's why I was saying that the test seems rather conclusive. (We'll leave aside the issue of whether this is a brother, or a cousin or the like, the Y test, at whatever number of markers, is not able to distinguish this, as all males in the family share the same Y).

Viceversa, if you take two random people, even a match at 67 would not be enough to establish an immediate relation (say within three or four generations). You need to look at autosomal tests. And for legal purposes, as said, you do need also an autosomal test.

cacio