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Archiver > GENEALOGY-DNA > 2003-12 > 1070743952


From: yair davidiy <>
Subject: Re: [DNA] Query on Haplogroups
Date: Sat, 06 Dec 2003 22:52:32 +0200
In-Reply-To: <18a.22fc0142.2d037df0@aol.com>


At 13:46 06/12/2003 -0500, you wrote:
>In a message dated 12/06/03 8:44:46 AM Pacific Standard Time,
> writes:
>
> > <<The more recent the
> > SNP, the more likely you are to find the same haplotype in different
> > haplogroups.>>
> > Ann Turner - GENEALOGY-DNA List Administrator
> >
> > Question: If genetic DNA change only occurs in one person and is then
> > transmitted through inheritance to others (as DNA scientists seem to say)
> > should not all haplotypes be in the same haplogroup?
> > The reality is (as far as I understand) that most haplotypes are mostly in
> > the same haplogroup but there are numerous exceptions as the above
> > sentence suggests.
>
>A SNP (Single Nucleotide Polymorphism) is a one-time event (or Unique Event
>Polymorphism) that defines the beginning of a new haplogroup. All the
>descendants of the person with the SNP will pass it on to the next
>generations.
>
>The person who has the SNP also has a haplotype, as defined by the Short
>Tandem Repeats that the genealogical companies test. This haplotype is the
>starting point for 100% of the descendants in the new group. STRs mutate more
>frequently, and the number of repeats can go up or down. The longer ago a SNP
>occurred, the greater the variety of haplotypes in the haplogroup.
>
>But the founding father of the new haplogroup probably had brothers and
>cousins of various degrees who had the same haplotype. Their descendants
>don't have
>the new SNP, so they stay in the old haplogroup, but they are starting with
>the same haplotype. Their descendants start accumulating variations in the
>haplotypes, too. The longer ago a SNP occurred, the more likely that the
>haplotypes have been diverging along different random pathways. The more
>recent the
>SNP, the more likely you are to find that some people have preserved the
>original
>haplotype. If the haplotype has been preserved, then all those people are
>"Identical by Descent" (IBD).

Thank you for your answer.
I understand up to here. Haplotypes and haplogroups are not family groups
but rather parallel markers with different
frequency of change.


>But people can also be "Identical by State" (IBS). That can happen when they
>start out with different haplotypes, but the mutations just happen to be in
>directions that make them more similar. Say for example, two people living
>a few
>hundred years ago had these haplotypes:
>
>11-11-11-11-12-13-11-11
>11-11-11-11-13-12-11-11
>
>Their common ancestor probably lived several hundred years or more earlier.
>If a descendant of person #1 has a mutation in the fifth marker that
>changes it
>to a 13, and a descendant of person #2 has a mutation that changes the sixth
>marker to a 13, then both people end up
>
>11-11-11-11-13-13-11-11
>
>That's called convergence. They are IBS, and it's just accidental that they
>end up with the same haplotype. That's not a practical concern over a
>genealogical time frame, however, since the mutations are rare to begin
>with, and the
>mutations would have to fall on exactly the right markers.
>
>Ann Turner - GENEALOGY-DNA List Administrator
>Search or Browse the archives, Subscribe or Unsubscribe at
>http://lists.rootsweb.com/index/other/Miscellaneous/GENEALOGY-DNA.html


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