GENEALOGY-DNA-L Archives

From: "Bob Durham, MHS" <>
Subject: [DNA] Y-Chromosome Test Standard Results Analysis
Date: Thu, 11 Jan 2001 14:44:47 -0800

After following the subject thread on this topic over the last few days, we
have added the following position statement to our initial Y-chromosome
calculator page:


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Y-Chromosome Test Standard Results Analysis:

In reponse to inquiries arising from the use of our Y-Chromosome Calculator,
Agenus offers the following information:

First, a quick Y-Chromosome primer:

"After mtDNA, the Y chromosome is by far the best studied genetic system in
human populations. The Y chromosome is inherited down the paternal line; in
this respect it complements mtDNA, although it differs in that it is passed
on only to sons, whereas mtDNA is passed on both to sons and daughters but
stops with the sons. So it is inherited in much the same way as surnames...
it can be analysed genealogically in much the same way as mtDNA. Until
recently it had the disadvantage that very little variation had been
found-now, however, researcher have identified both slowly-evolving base
variants and fast-evolving microsatellite markers on the Y. Microsatellites
are repeats of short stretches of a small number of bases, such as the
2-base pair repeat CTCTCTCTCT..., or the 4-base repeat ATTGATTG.... The
slowly-evolving base variants, defining haplogroups as with the mtDNA, can
be used to build up gene trees, and the microsatellites are useful for
higher genealogical resolution and dating." - Martin Richards, PhD Lecture 2

As you can see from the Martin Richards narrative, base pair repeats are the
basis of Y-Chromosome analysis because the Y-Chromosome has a low rate of
mutation. More specifically, the number of repeats at a specific
y-chromosome loci is the most 'efficient' format to achieve a standardized
representation of results from short tandem repeats (STR) analysis. This is
because it offers a tangible measurement that is repeatable. While sequence
data would be ideal, it is much harder to get good sequences in these
repeated regions; consequently it is more laborious and expensive to obtain.
By comparison, DNA laboratories have used the number of repeats in STRs as a
standard for years to determine biological relationships such as paternity,
siblingship, and matching identities in cases of forensic testing. Discrete
alleles from STR systems may be obtained due to their smaller size, which
puts them in the size range where DNA fragments differing by a single
basepair in size may be differentiated. Determination of discrete alleles
allows results to be compared easily between laboratories without binning.

The Agenus.com Y-Chromosome Calculator is based on analyzing base pair
repeats data in the most standardized and tangible format possible. The
process allows selection of STR loci and relevent alleles (enumerated
repeats), all of which should be documented within the Y-Chromosome test
results you receive from a laboratory. This deliberate approach to a
standard analysis model facilitates comparing test results between
laboratories over time. In addition, we believe it foster's a collaborative
use of collective results to the benefit of each individual tested. Finally,
from a research perspective the use of standard Y-Chromosome test results
will expand the scope and accuracy of conclusions made against the data.
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We hope this helps to explain our approach to the issue of analyzing
Y-chromosome test results.

Consummate regards,
Bob Durham, MHS
Chief Executive Officer
Agenus Incorporated
660 Baker Street, Suite 405
Costa Mesa, CA 92626
Phone: 1.714.432.9705
FAX: 1.714.641.2707
www.agenus.com

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