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 divisions 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 organ-
ism;[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 biology is
the process of cellular differentiation. During
morphogenesis, totipotent stem cells become
the various pluripotent cell lines of the em-
bryo which in turn become fully differenti-
ated 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 con-
tinues to divide. It does so by activating some
genes while inhibiting others.[3]
Etymology and
definitions
According to Dr. Steve Folmar, the word epi-
genetics has had many definitions, and much
of
the confusion surrounding
its usage
relates to these definitions having changed
over time. Initially it was used in a broader,
less specific sense but it ha