Download epigenome

Same DNA, Different Cells



DNA contains the
instructions for
building all parts of
the body.
Every one of your
cells has the same
DNA code and it
doesn’t change over
your lifetime.
Then what makes a
skin cell different from
a muscle cell different
from a nerve cell?
…GENE EXPRESSION!
Different sets of active
genes allows cells to
use the same genetic
code in different
ways.
 Fun fact: only 10-20%
of genes are active in
a differentiated cell

What is EPIGENETICS?
Certain parts of your DNA are
turned on (activated) and off
(deactivated) at specific times
and in specific locations by
various chemical reactions.
 Epigenetics = the study of these
chemical reactions and the
factors that influence them.

How does epigenetics work?
DNA is wrapped around proteins called
histones.
 Both the DNA and histones are covered
with chemical tags

 This second layer of structure = the epigenome
 The epigenome shapes the physical structure of
the genome (all of your DNA)
Epigenetic tags turn genes on & off
without changing the genetic code

Inactive genes = tightly wrapped … makes
genes unreadable/silenced
 METHYL GROUPS ATTACHED

Active genes = relaxed/unwound … makes
genes accessible/readable
 ACETYL GROUPS ATTACHED
Your epigenome CAN change
Your DNA doesn’t change over your lifetime,
but your epigenome can change.
 Epigenetic tags react to signals from the
outside world such as:

 Diet
 Stress
 Physical activity
 Toxins
Identical Twin Studies
Identical twins have the same DNA since
they came from a single fertilized egg.
When they’re born, they have the same
epigenome (chemical tags on their DNA).
 Over time, identical twins become
increasingly different. Why?

Identical Twin Studies

Their environments
change. Signals
from the
environment act on
the epigenome that
active/silence
different genes.
 Diet, physical activity,
exposure to toxins,
stress
Epigenetic example: Lick your rats!
Rat pups who are highly nurtured by their
mothers (licked, groomed, nursed) tend to
grow up to be calm adults.
 Rat pups who receive little nurturing tend to
grow up to be anxious.

Epigenetic example:
Genetically
identical, but
Agouti mice
epigenetically

All mammals have a
gene called agouti. In
mice, when the agouti
gene is…
 unmethylated - it has a
yellow coat, is obese, and
prone to diabetes and
cancer.
 methylated - (normal mice)
it has a brown coat, and a
low disease risk.
different
Epigenetic example: Agouti mice
Pregnant yellow mice fed a methyl-rich diet
produced mostly brown (normal) pups.
 Take-home message: The environment in the
womb can influence adult health.
