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From:
Subject: Re: [DNA] Some thoughts about the near future--how many STRs??
Date: Sat, 3 Apr 2004 11:43:06 EST
In a message dated 03/28/04 9:05:45 PM Pacific Standard Time,
writes:
> Does anyone out there know how many STR loci exist in an average
> Y-chromosome? Of course, we'll have to define an STR loci, for example a
> site on the Y-chromosome where about 3 nucleotides are repeated at least 6
> times.
Mark Jobling's paper "The Human Y Chromosome: an Evolutionary Marker Comes of
Age" came out last year, soon after the "complete" sequence of one man's Y
chromosome was published. Actuallly, less than half of the total length was
sequenced, but the unmapped portion is full of repetitive DNA sequences with very
few landmarks to anchor them.
I've recommended the article in several different contexts -- it is a
treasure trove of information.
http://www.le.ac.uk/genetics/maj4/JoblingTS.03.NRG.Review.pdf
The published sequence can be searched with a computer program for STRs
(Short Tandem Repeats, also called microsatellites). There are ~ 100-200
"potentially useful" new microsatellites. The actual utility depends on studying them in
various populations to see if they vary and if they have a useful mutation
rate.
> Are the majority of people upgrading from 25 to 37 really gaining much
> benefit, or have most already got about all they need to know at 25?
It's too soon to tell, as very few people have reported their results, but
there is the law of "diminishing returns." Going from 12 to 25 shows a dramatic
difference in narrowing the time frame for the Most Recent Common Ancestor;
going from 25 to 37 doesn't help as much.
http://dnaheritage.com/markers.asp
Ann Turner - GENEALOGY-DNA List Administrator
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