[Ger-Poland-Volhynia] 23andMe DNA testing

Keith Trott trottkg at telus.net
Thu Nov 10 20:25:56 PST 2011

It seems to me that they are going about it incorrectly.  Meiosis does cause
mixing of genetic material from both parents but mitochondrial DNA comes
only from the mother.  So this is the DNA that should be analysed if you are
going to trace you maternal linage.  On the other hand only the last 6 to 8
genes on the Y chromosome have capability to recombine so if you want to
trace your paternal linage you should be looking at the remainder of the Y

If you want to bone up on genetics, may I suggest
http://www.hhmi.org/biointeractive/disease/finlay_bio.html?  Click on
lectures --> Holiday Lectures --> then Genomics and Chemical Genetics or Sex
Determination or a number of other very stimulating lectures, IMHO.

-----Original Message-----
From: Vince Tilroe [mailto:vtilroe at gmail.com] 
Sent: Tuesday, November 08, 2011 3:50 PM
To: ger-poland-volhynia at eclipse.sggee.org
Subject: Re: [Ger-Poland-Volhynia] 23andMe DNA testing

Hi Gail,

You can find me as "zurgleblatz" at 23andMe.

mt-DNA is passed down from mother to child, but only females transmit it to
their offspring.

Y-DNA is only passed from father to son.

The other 22 pairs of chomosomes are called "autosomes", which are
transmitted to both females and males, but each pair of chromosomes
undergoes recombination during each meiosis (occurring in the production of
egg and sperm cells).  The X-chromosome is a bit different in that females
inherit one from each parent (and will recombine when they produce their own
egg cells), but males receive their single copy from their mother.

23andMe's Relative Finder tool uses all 22 pairs of autosomes and the
X-chromosome(s).  There is a bit of a caveat, in that the process of
recombination diminishes the percentage of autosomal DNA inherited from an
ancestor, i.e. on average, 50% comes from each parent, 25% from each
grandparent, 12.5% from each great-grandparent, 6.25% from each 2nd
great-grandparent, and so on.  Thus two siblings will share 50% on average,
a nephew/niece and aunt/uncle will share about 25%, first cousins will share
about 12.5%, and so on.  Thus where more than 10 generations (meiotic
events) exist between any two people (i.e. their shared DNA is a miniscule
fraction of a percent), the certainty of the degree of a possible genetic
relationship can get fairly dodgy and circumstantial.

Please see http://www.isogg.org/wiki/Relative_Finder for more information.

Hope this helps,

Vince Tilroe

> There was a discussion a few weeks back about 23andMe having a special.
>  Several people said they had their DNA testing done through them and 
> had the results on the website.  I have my results back and would like 
> to see if I could compare with any others on the group.  I am female and I
> we can only compare the MtDNA?   Not sure how all this works.
> Gail

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