What is Epigenetics?

Epigenetics literally means “on” genes.  It’s an area of
science that deals with all modifications to genes excluding
changes in the DNA sequence itself.  (When a cell divides, an
error could occur when transcribing the information to the
daughter cell; this is called a mutation and should not be
confused with epigenetics).  Epigenetics modifications include
addition of molecules, like methyl groups, to the DNA structure.
Adding these components changes the appearance and structure of
DNA, it will change how it relates to important transcribing
molecules in the cell’s nucleus.

Importance of Epigenetics

By nature, the genome is largely static; epigenetics
modifications on the other hand introduces a measure of
flexibility to the process; they provide a necessary dynamic
variability to cellular function and phenotype, allowing for
cellular differentiation.  Epigenetics may also play a role in
evolution, epigenetic modifications can be passed on to future
generations.  Often, however, these modifications are lost after
several generations.  (Contrast with genetic modifications which
do not disappear).

As will be pointed out (under Methylation and Histones),
epigenetic modifications, or “marks,” impact on how genes can
interact with the cell’s transcribing mechanism.  Marks can turn
genes on or off, allowing or preventing the genes from
synthesizing a protein.

Silencing of Genes

Picture a top management meeting in a given corporation.
The president, vice-presidents, and some key personnel are
meeting to discuss a difficult problem and hopefully find a
solution.  What is the most important thing that should be
observed during such a meeting?  Silence!  I don’t mean that
total silence should prevail, simply let the expert in a given
area express his views without interference.  When the vice-
president in charge of marketing speaks, there should be total
silence with everybody else carefully listening to what he has to
say.  I can see you smiling already, that doesn’t happen in real
life.  Even if the president has demanded total silence, nothing
stops the other attendees from going, in their own mind, in a
different direction.  Listening carefully?  Not a chance!  This
is contrary to human nature.  The body, however, cannot afford a
cacophony.

Silencing of genes is nature’s way of giving each cell a
complete set of genes, and having organs perform specific
functions.  With some 30,000 genes in the human genome, selective
silencing is critical.  The stomach cells that produce
hydrochloric acid should not be turned on in the brain!

This process is governed by epigenetics factors.
Methylation, the addition of a methyl group, plays a role in all
sort of phenomena in which genes are switched on or off, for
instance, the growth of cancerous tumors.  Hypermethylation can
interfere with tumor suppressor genes.  Such epimutations has
been observed in many cancers.  This open the way for the
treatment of some cancers.  We’re not there yet, but epigenetics
could provide us with a weapon to fight an implacable foe.

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