Download Epigenetics

Why are some genes
expressed and not others?
Epigenetics
WHAT IS EPIGENETICS?
“The development and maintenance of an
organism is orchestrated by a set of chemical
reactions that switch parts of the genome off and
on at strategic times and locations.”
“Epigenetics is the study of these reactions and
the factors that influence them.”
From http://teach.genetics.utah.edu/
DNA wrapped around histones with
methyl (green) and acetyl (red)
groups controlling how tightly they
are wrapped
So How
Does this
Work
Chemically?
What should you be able
to do?
Describe the physical state
of the genome (tightly
wrapped, or relaxed)
when genes are inactive.
Describe the physical state
of the genome when
genes are active.
The epigenome marks your genome in two
ways, both which may turn genes off or on.
• The first type of mark, called DNA methylation,
directly affects the DNA in your genome. This can
also occur with acetylation.
• In this process, chemical tags called methyl
groups attach to the backbone of the DNA
molecule in specific places.
• The methyl groups turn genes off or on by
affecting interactions between DNA and the cell's
protein-making machinery.
•
http://www.genome.gov/27532724
• The second kind of mark, called histone modification,
indirectly affects the DNA in your genome.
• Histones are proteins which enable DNA's molecules
to be wound up neatly into chromosomes inside the
cell nucleus.
• A variety of chemical tags can grab hold of the tails
of histones, changing how tightly or loosely they
package DNA.
• If the wrapping is tight, a gene may be hidden from
the cell's protein-making machinery, and the gene
may be switched off.
• In contrast, if the wrapping is loose, a gene that was
formerly hidden may be turned on.
So who would make a good model
for epigenetics?
How about identical twins?