Methylation

DNA methylation is the addition of a methyl group to
specific bases in the DNA sequence.  A methyl group includes 1
carbon atom + 3 hydrogen atoms (-CH3).

Startling scientific discoveries have recently revealed that
single nutrients, toxins, behaviors or environmental exposures
can silence or activate a gene without actually altering its
genetic makeup.

For instance, environmental exposure initiate a chemical
modification that mobilizes a methyl group.  In turn, the methyl
group attaches to the control segment of a gene and either
silences it or alternately activates it.  One way or the other,
the gene is compelled to change its normal activity

Methylation plays an important role in plants.  More will be
said on that in the section on plants.

Histones

The DNA is tightly wound around proteins known as histones.
When the time comes to transcribe the genetic information, the
cell needs to unwind its DNA in order to make it available to the
RNA.  Alterations to this structure cause certain genes to be, or
not to be, available to the cell’s chemical mechanism and thus
determine whether those genes are expressed or silenced.

As already noted, DNA methylation will do the same thing,
but presumably under different circumstances.

“Junk” DNA

When the human genome was mapped out, we discovered that we
differ from one another (regardless of environment, nationality,
or race) by a tiny fraction of 1%; I believe less than 1/10 of
1%!  A further blow to our ego is that we differ from chimpanzees
by about 2%!  But the biggest surprise was that only 2% of our
DNA – via RNA – codes for proteins; the rest was considered
“junk,” the leftover is the result of million of years of
evolution.

Now that epigenetics is becoming a bona fide science, with
more interest from the scientific community, scientists are
discovering that some of this junk DNA switches on RNA that may
do the work of proteins and interact with other genetic material.

Introducing Flexibility

The genes identified by the human genome project are now
widely viewed as a set of instructions for the human body.  But
genes themselves need instructions for what to do, and where and
when to do it.  Remember that genes in all the cells of a given
individual are identical.  Moreover, I explained that gene
silencing or activation is part of the operation; as well, I
pointed out that this process is part of the job description of
the epigenes.  And it’s a good thing!  Genes are largely cast in
stone, the epigenome (an array of chemical markers and switches),
lie along the length of the double helix.  These epigenetics
markers and switches turn on and off the expression of particular
genes.  They introduce needed flexibility to the genetic package.
Think of the genome as your computer, it’s hardwired, without
software it can do a limited number of tasks.  The epigenome on
the other hand is the software, it allows your genes to do so
much more (i.e. produce a variety of proteins, etc.).  It allows
you to adapt to various conditions and circumstances.  It
introduces flexibility to the human body.  (This point will be
made in many different ways in the coming parts.  By the time
you’re through, you’ll wonder how come science has been blind for
so long to this important biological phenomenon).

Sources

1) The U.S. Human Genome Project
www.ornl.gov/sci/techresources/2Human_Genome/project/about.shtml

2) How epigenetics shapes life
www.scienceinschool.org/2006/issue2/epigenetics/

3) Backgrounder:  Epigenetics and Imprinted Genes
www.hopkinsmedicine.org/press/2002/november/epigenetics.htm

4) Epigenetics:  The Science Of Change
www.ehponline.org/members/2006/114-3/focus.html

5) Importance of epigenetics
www.epidna.com

6) Epigenetics
A new science peels away another layer of the genetic onion
By John McManamy
www.mcmanweb.com/epigenetics.html

7) Duke University Medical Center (2005, October 27).
“Epigenetics” Means What We eat, How We Live And Love, Alters How
Our Genes Behave
www.sciencedaily.com/releases/2005/10/051026090636.htm

8) DNA Is Not Destiny
The new science of epigenetics rewrites the rules of disease,
heredity, and identity
By Ethan Watters
Published online November 22, 2006
http://discovermagazine.com/2006/nov/cover

9) It’s all in the epigenes
By Daniel Tencer
The Ottawa Citizen
August 26, 2006

Site Search Tags:
none