[ SHOWGSD-L ] Why Genes Aren't Destiny
- From: "Cyndi Flautt" <caretti1@xxxxxxxxxxx>
- To: <showgsd-l@xxxxxxxxxxxxx>
- Date: Wed, 8 Sep 2010 23:00:45 -0500
With all of the talk about inbreeding/outcrossing, etc, I thought I'd write
about an article from the Jan 2010 issue of Time magazine. I've been
meaning to post about it for some time but just haven't taken the
time.....The title of the article is "Why Genes Aren't Denstiny"....The new
field of epigenetics is showing how our environment and your choices can
influence your genetic code--and that of your kids.
Excerpts from the article..............Genes contain the codes for cells to
produce the various proteins that organisms need to function......Just as
genes provide the codes for producing proteins, various chemicals called
epigenetic marks sit atop genes and offer basic instructions to them,
telling them to switch on or off. All cell types- muscle cells, nerve
cells, etc- contain the exact same DNA. Epigenetic marks silence certain
gene sequences and activate others so that nascent cells can differentiate.
It the marks don't work properly, cancer or cell death is possible.
...Stressors like a rich diet can activate epigenetic marks, modifying
histones or adding methyl groups to DNA strands. These changes can turn
genes on or off and may affect what gets passed down to your offspring.
.....If you overstimulate genes for, say, obesity or a shortened life span,
your kids can inherit these overactivated sequences. That could mean a
lifetime of battling unfavorable gene expression. ...............As
momentous as epigenetics sounds, the chemistry of at least one of its
mechanisms is fairly simple. Darwin taught us that it takes many
generations for a genome to evolve, but researchers have found that it takes
only the addition of a methyl group to change an epigenome. A methyl group
is a basic unit in organic chemistry. When a methyl group attaches to a
specific spot on a gene, it can change the gene's expression, turning it off
or on, dampening it or making it louder. .....In 2003, a study was done at
Duke University with mice with a uniquely regulated agouti gene- a gene that
gives mice yellow coats and a propensity of obesity and diabetes when
expressed continuously. The team fed one group of pregnant agouti mice a
diet rich in B vitamins. Another group of genetically identical pregnant
agouti mice got no such prenatal nutrition. The B vitamins acted as methyl
donors: they caused methyl groups to attach more frequently to the agouti
gene in utero, thereby altering its expression. And so without altering the
genomic structure of mouse DNA, simply by furnishing B vitamins- the
researchers got agouti mothers to produce healthy brown pups that were of
normal weight and not prone to diabetes..........Other recent studies have
also shown the power of environment over gene expression. For instance,
fruit flies exposed to a drug called geldanamycin show unusual outgrowths on
their eyes that can last through at least 13 generations of offspring even
though no change in DNA has occurred (and generations 2 through 13 were not
directly exposed to the drug) ............Can epigenetic changes be
permanent? Possibly, but it's important to remember that epigenetics isn't
evolution. It doesn't change DNA. Epigenetic changes represent a
biological response to an environmental stressor. That response can be
inherited through many generations via epigenetic marks, but if you remove
the environmental pressure, the epigenetic marks will eventually fade, and
the DNA code will- over time- begin to revert to its original programming.
That's the current thinking: that only natural selection causes permanent
genetic change.
.............OK, that's your science lesson for the year!!.....Relating this
to breeding GSD's.....are we selecting genes...or genetic sequences that
have been altered by positive (or negative) epigenetic marks???!!
....or both?!
Interesting..............
~Cyndi Flautt
www.carettigsd.com
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