Okay, here's the skinny.
DNA is comprised of strings of 4 molecules abbreviated to A, C, G, and T.
(You can look up the long names. I'll never memorize them).
They are arranged in strings with a total of something like 3 billion
"bases."
The Y chromosome is the puny chromosome. It doesn't do much but hold the
male sex gene. Because of that, it is continually getting smaller. There's
so little good information that when it sloughs some of it off, it gets
passed down with no ill effect and so just keeps propagating, with
changes, through the generations--as opposed to killing the inheritor. (So
far this is sounding a lot like the perfect analogy to men.)
Geneticists have found that specific areas of this "junk" dna have
specific patterns that repeat X number of times. For example, at loci 21,
I have the sequence of T-T-T-C repeated 34 times. All the other Cooleys of
our clan who have tested have only 33 repeats (literal repeats) of
T-T-T-C.
http://ancestraldata.com/ahnentafel/256/ydna.html
Because this "mutation" is among the "junk" DNA, it doesn't provide
instruction for the creation of proteins (as genes do) and I did not grow
an extra finger on my forehead. These mutations are totally benign and are
ignored in the process of natural selection. (Some mutations are not
benign. For example, a friend's son was found to have cancer at the age of
10 months. This was due to a random mutation in a critical gene on one of
the other chromosomes. These children do not live to maturity, so the gene
is not passed to children; it remains very rare. Only about 4 children are
born each year in the US with that mutation.)
Joseph's Mike Cooley (Mary's husband) has only ten repeats at loci 4. It's
the only mismatch among the first 12 markers we see in all twelve Cooleys
who have tested. These 12 markers are more stable and tend to mutate less
frequently than the others. Since it's possible it's an older mutation
than the others (in fact, it could have been acquired in any generation)
there's a small chance that Joseph himself or perhaps his son Jackson had
already acquired it. I'd sure be interested in see another Joseph
descendant test. :)
Clear as mud?
-Michael
Received on Sun Jul 15 2012 - 16:02:20 MDT