GENEALOGY-DNA-L Archives

Archiver > GENEALOGY-DNA > 2001-02 > 0982874196


From: Terrence Carmichael <>
Subject: Re: [DNA] Anyone for Pie?
Date: Thu, 22 Feb 2001 12:36:36 -0800
References: <85.737297b.27c6b123@aol.com>


Not really, Richard. The DNA is still there, and intact. If you look at ALL of
your ggggggg-grandparents you will find ALL of your DNA!! Where else would one
expect the DNA could come from, spontaneous combustion (ha ha)? Even recombination
between chromosomes still does not account for a loss or gain in your DNA. 100% of
your DNA can still be found in ALL of your gggggggg-grandparents (okay, given a
small number of changes do to mutations, which will only influence a very tiny
amount of your total, physical DNA)!!

Now, when you are comparing phenotype (distinguishable characteristics such as eye
color, statue, hair, etc.) to genotype (physical DNA characteristics), it is
important to understand that the genotype, which is contributing to the phenotype,
is the part of your DNA that will show much lower rates of mutation over
generations (because they are necessary to produce a viable organism -the genes)
than the 'junk DNA' (STRs, LTRs, etc.) that we examine when doing Y-chromosome
analysis, paternity testing, and etc.

Remember that both you and me, and both of our gggggggggg-grandparents, and their
next door neighbors, all share 99.9999% of our DNA. That is to say that 99.9999%
of our DNA is identical!! Actually, we share more than 98% of our DNA with the
orangutan, our (arguably) very distant relative. So, how do we measure what DNA
came from which ancestor when we are so much alike? Well, most the DNA is
identical to begin with, so we can really only measure possibly less than 0.00001%
of the total DNA. In my opinion, I believe that SNP-typing is the way to go if you
are looking at very distant relatives. Microarrays developed to characterize 1000s
of SNPs will allow us to more accurately determine relationships between distant
relatives by examining not only Y and mtDNA, but also the autosomal DNA.

Mark Usher talked about dominance, co-dominance, recessive genes, etc., which do
not really have a place in your chart because you are talking about total DNA, not
the distinguishable characteristics such as eye color, statue, hair, etc.
(phenotype), that Mark is referring to in his Resemblance Test. Therefore, even if
a gene's expressed phenotype is masked by another (dominant) gene, the DNA is
still present. Furthermore, if the masked gene is passed on to another generation
it may be expressed. An example of how traits can skip generations.

If anyone would like to better understand inheritance, and genotype vs. phenotype,
study the work of Fr. Gregor Mendel, an Augustinian monk, who (in the 1800s)
measured phenotypic breeding patterns of the common garden peas to conclude two
laws of genetics, and be the first to describe the gene as the unit of
inheritance.

Terry

Anyone for Pie? -I will take a slice of the Apple, with vanilla ice cream!

<<<<
It seems like I remember reading somewhere that by the time one gets back to
their 7th, 8th, 9th generations and earlier, almost all of the DNA from these
generations has undergone so much reshuffling and such, that it is
essentially lost, or at least suppressed by one's more recent generations.
Would that be accurate to say?

Richard
>>>>

wrote:

> In a message dated 2/22/01 12:55:00 PM, writes:
>
> <<Nice chart, Richard!
>
> Statistically speaking, I believe that these numbers are pretty accurate for
>
> autosomal DNA, and give a nice representation of what we would expect to see
>
> through the inheritance of genetic material. However, it is important to
> understand
>
> that you could have inherited as much as 50% of your grandfather's autosomal
> DNA,
>
> and as little as 0%.
>
> If you think about it, you could even have inherited 50% of your
>
> g-g-g-grandfather's DNA. Although it is unlikely, it can happen. This may be a
>
> reason why some people do resemble their g-g-g-g-grandparents. Anyone that
> has paid
>
> attention in statistics will know that deviations from the norm do occur. I
>
> remember once, while on a plane heading to Las Vegas, I was testing my wife's
> luck
>
> by flipping a coin and having her guess heads or tails. I flipped that coin 22
>
> times, and got heads every time. My wife kept on guessing tails (she scored
> very
>
> low on the good luck chart!). This is why doubling up on your bets can make
> you go
>
> broke!! In the same way, you can lose all your inheritance (no pun intended).
>
> Therefore, I think that you should say ...
>
> If 100% of the pie represents you and your DNA, then:
>
> You received 100% from your parents (statistically, 50% from each)
>
> 100% from your grandparents (statistically, 25% from each)
>
> 100% from your great-grandparents (statistically, 12.5% from each)
>
> 100% from your 2nd-great-grandparents (statistically, 6.25% from each)
>
> 100% from your 3rd-great-grandparents (statistically, 3.125% from each)
>
> With respect to DNA inheritance, I believe that it is interesting to
> understand
>
> that 2 full-siblings can share as much as 100% of their DNA and as little as
> 0%
>
> (excluding mtDNA and the X and Y chromosomes).
>
> In conclusion, my cousin looks nearly identical to our g-g-g-grandfather, and
> I
>
> think that genetics has something to do with it. I would say that he has about
>
> 21.43% of our g-g-g-grandfather.
>
> Best regards,
>
> Terry
>
> >>
>
> Thanks for a good explanation Terry. I think some of this stuff is starting
> to sink in!
>
> It seems like I remember reading somewhere that by the time one gets back to
> their 7th, 8th, 9th generations and earlier, almost all of the DNA from these
> generations has undergone so much reshuffling and such, that it is
> essentially lost, or at least suppressed by one's more recent generations.
> Would that be accurate to say?
>
> Richard
>
> ==============================
> Shop Ancestry - Everything you need to Discover, Preserve & Celebrate
> your heritage!
> http://shop.myfamily.com/ancestrycatalog

This thread: