Epigenetics
This article is part of the series on:
Gene expression
a Molecular biology topic (portal)
(Glossary)
Introduction to Genetics
General flow: DNA > RNA > Protein
special transfers (RNA > RNA,
RNA > DNA, Protein > Protein)
Genetic code
Transcription
Transcription (Transcription factors,
RNA Polymerase,promoter)
post-transcriptional modification
(hnRNA,Splicing)
Translation
Translation (Ribosome,tRNA)
post-translational modification
(functional groups, peptides,
structural changes)
gene regulation
epigenetic regulation (Hox genes,
Genomic imprinting)
transcriptional regulation
post-transcriptional regulation
(sequestration,
alternative splicing,miRNA)
post-translational regulation
(reversible,irrevesible)
In biology, the term epigenetics refers to changes in
phenotype (appearance) or gene expression caused by
mechanisms other than changes in the underlying DNA
sequence, hence the name epi- (Greek: over; above)
-genetics. These changes may remain through cell divi-
sions for the remainder of the cell’s life and may also last
for multiple generations. However, there is no change in
the underlying DNA sequence of the organism;[1]
instead, non-genetic factors cause the organism’s genes
to behave (or "express themselves") differently.[2] The
best example of epigenetic changes in eukaryotic bio-
logy is the process of cellular differentiation. During
morphogenesis, totipotent stem cells become the vari-
ous pluripotent cell lines of the embryo which in turn
become fully differentiated cells. In other words, a single
fertilized egg cell - the zygote - changes into the many
cell types including neurons, muscle cells, epithelium,
blood vessels et cetera as it continues to divide. It does so
by activating some genes while inhibiting others.[3]
Etymology and definitions
According to Dr. Steve Folmar, the word epigenetics has
had many definitions, and much of the confusion sur-
rounding its usage relates to these definitions having
changed over time. Initially it was used in a broader, less
specific sense but it has