◦ Epi-: Greek root meaning upon, over, or above
◦ Epigenome: A system whereby individual gene
sequences (stretches of DNA) could be turned
on or off or made to function at higher or lower
◦ Epigenetics: Modifications of the genome,
heritable during cell division, that do not involve
a change in the DNA sequence.
Epigenetics simply meant “developmental
genetics,” i.e, the study of the way the DNA code
of genes is translated into the bodies and
physiologies of organisms.
It involves understanding how genes are turned
on and off in different tissues and cells,
How different genes interact with each other, and
how the products of a one-dimensional sequence
of information can build a three-dimensional
The second meaning of “epigenetics” is more
recent, and involves actual changes in the DNA
itself that are not based on mutational changes in
nucleotides, but in environmental modifications
of nucleotides—things like methylation of
nucleotide bases or changes in DNA-associated
proteins like histones—that can temporarily
modify genes and affect their actions.
The list of covalent modifications to histone
proteins continues to grow. (Review by T.
However, only recently has genetic and
biochemical evidence converged to clearly
connect covalent histone modifications with
longstanding epigenetic phenomena.
Drosophila genetics provides another link
between epigenetics and histone
modifications, in the form of two
evolutionarily conserved families of proteins
that regulate homeotic genes antagonistically
during development: the Polycomb Group
(PcG) and the Trithorax Group (TrxG).
Recently, it has become evident that RNA,
particularly non coding RNAs, have a hand in
controlling multiple epigenetic phenomena
(Bernstein and Allis, 2005).
There is not the slightest evidence that the findings
of epigenetics will dispel the main ideas of neo-
Darwinism, which include
The ideas of evolutionary change via natural selection
and genetic drift
The randomness of mutations,
The ideas of speciation and common descent, and
The gene-centered view of evolution.
There are several definitions of “epigenetics”
(it once meant simply “development”), but
Burkeman uses the term in its more modern
sense as “inheritance not based on coding
changes in the DNA.”
Burkeman cites a couple of recent studies in
which nongenetic, developmentally caused
changes in an organism (like alterations in
physiology due to starvation) can be passed
on to one or two generations of its
The offspring of stressed Swedish chickens,
for example, have difficulty navigating
There is random variation of phenotypic
There is some ecological variable that is
sensitive to the strength of the correlation of
such traits with fitness.
There is some mechanism that alters the
relative frequency of the trait in the
population so that, all else equal, it varies
with the strength of the correlation between
the trait and fitness.
For example, suppose random variation
produces a trait that tends to make its
bearers invisible to their predators.
Then, all else equal, the predators gobble up
the creatures that don’t have it, and the
relative frequency of the trait in the
population increases from generation to
• The experiment also found that 166 fathers in the
study had started smoking before age 11 (right before
the body goes through puberty)
o Sperm could have been effected by epigenomes,
changed by the early smoking.
• Sons of the 166 fathers on average had a higher BMI
than other children
• Scientist are further researching Epigenetics because, if
they are able to be controlled, it would be helpful in the
o Trying to develop medicine that is able to turn off a
negative epigenome and turn on a positive one.
In 2004--the first epigenetic drug was
Treats deadly blood tumors/cancers etc.
Life expectancy is expanded by 9 months+
• Scientists are trying to develop other medicines
that manipulate epigenomes for Cancer,
Schizophrenia, Autism, Alzheimers, Diabetes, etc.