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From:
Subject: Re: [DNA] Gene for Lactose Intolerance Identified
Date: Sat, 4 Jun 2005 12:02:52 EDT


In a message dated 6/3/05 6:26:36 PM Pacific Daylight Time,
writes:

> http://www.newscientist.com/article.ns?id=dn1787
>
> Couldn't this test, if as inexpensive as the article states, be used for
> genealogical genetic testing? To give a clue as to one's origin much as the
> Duffy null is used now? I understand that the presence of Duffy null is included
> in the DNAPrint.
>

Yes, it could be used in a test like DNAPrint, although I have the impression
that many, if not most, of DNAPrint's markers use "junk" DNA and therefore
have no phenotypic (i.e. observable) consequences. The Duffy gene would be an
exception.

There was a very strong selective advantage from the mutation for lactase
persistence, so that particular mutation spread quickly throughout the range
where descendants of the founder migrated, and it would indeed make a good marker
for European vs all other populations.

There are other mutations for lactase persistence in other populations (see
abstract below my signature), so two people having the *trait* of lactose
tolerance would not necessarily have a common ancestor for it. You would need to
test for specific SNPs.

Under the assumption that DNAPrint's SNPs are Unique Event Polymorphisms
(UEPs), any of their markers could be used as pointers to a common ancestor within
xx thousand years for people who have the derived (mutatnt) allele. Those who
have the ancestral version of the marker would also have common ancestors,
but they could theoretically predate the origin of Homo sapiens.

Ann Turner


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Am J Hum Genet. 2001 Jan;68(1):160-172. Epub 2000 Nov 28.

Lactase haplotype diversity in the Old World.

Hollox EJ, Poulter M, Zvarik M, Ferak V, Krause A, Jenkins T, Saha N, Kozlov
AI, Swallow DM.

MRC Human Biochemical Genetics Unit, Galton Laboratory, Department of
Biology, University College London, London NW1 2HE, United Kingdom.

Lactase persistence, the genetic trait in which intestinal lactase activity
persists at childhood levels into adulthood, varies in frequency in different
human populations, being most frequent in northern Europeans and certain
African and Arabian nomadic tribes, who have a history of drinking fresh milk.
Selection is likely to have played an important role in establishing these
different frequencies since the development of agricultural pastoralism approximately
9,000 years ago. We have previously shown that the element responsible for the
lactase persistence/nonpersistence polymorphism in humans is cis-acting to
the lactase gene and that lactase persistence is associated, in Europeans, with
the most common 70-kb lactase haplotype, A. We report here a study of the
11-site haplotype in 1,338 chromosomes from 11 populations that differ in lactase
persistence frequency. Our data show that haplotype diversity was generated
both by point mutations and recombinations. The four globally common haplotypes
(A, B, C, and U) are not closely related and have different distributions; the
A haplotype is at high frequencies only in northern Europeans, where lactase
persistence is common; and the U haplotype is virtually absent from
Indo-European populations. Much more diversity is seen in sub-Saharan Africans than in
non-Africans, consistent with an "Out of Africa" model for peopling of the Old
World. Analysis of recent recombinant haplotypes by allele-specific PCR, along
with deduction of the root haplotype from chimpanzee sequence, allowed
construction of a haplotype network that assisted in evaluation of the relative
roles of drift and selection in establishing the haplotype frequencies in the
different populations. We suggest that genetic drift was important in shaping the
general pattern of non-African haplotype diversity, with recent directional
selection in northern Europeans for the haplotype associated with lactase
persistence.

PMID: 11095994 [PubMed - indexed for MEDLINE]

http://www.journals.uchicago.edu/cgi-bin/resolve?AJHG002187PDF

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