GENEALOGY-DNA-L Archives

From:
Subject: Re: [DNA] How Specific is 12 marker test [randomness]
Date: Fri, 30 Aug 2002 10:57:21 EDT

In a message dated 08/29/02 8:01:46 PM Pacific Daylight Time,
writes:


> We have a second set of brothers who are absolutely identical. This is why
> I made the observation some time back that it appears to me there is
> something at work with regard to mutations other than JUST generational
> relationships. But what it may be I have no clue. Why do we see two
> mutations in one generation of one family and none in 50 birth events in
> another? What makes the markers so stable in one instance and instable in
> another?

I know that some markers are notoriously unstable. I know that BYU abandoned
use of DYS310 for this reason. I don't know the structure of DYS310, but I
have read that one the number of repeats reaches a certain threshhold, say 50
repeats, the STR becomes more unstable.

http://www.ncbi.nlm.nih.gov/books/bv.fcgi?tool=bookshelf&;
call=bv.View..ShowSection&searchterm=mutations&
rid=iga.section.d1e59215#d1e59712

But for other markers, random events can account for many scenarios.
Newspapers often report "cancer clusters," but if you run a random number
generator to plot points on a map, you can often see what looks like
clusters, 4 "cases" in one region and none in another region. Remember that
randomly distributed does not mean evenly distributed. You would need to have
a very large data set before you could conclude with confidence that one
family line has more mutations than another.

Ann Turner
GENEALOGY-DNA List Administrator
http://lists.rootsweb.com/index/other/Miscellaneous/GENEALOGY-DNA.html
DNA preservation kits: http://www.dnafiler.com

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