posted on Feb, 22 2014 @ 02:10 PM
reply to post by Phage
RE: Epigenetics is all about override.
Yes, epigenetics affects some gene expression.
And without genes, there is no genetic expression to talk about. So, it is a matter of genetic inheritance.
Like our different cells do, we all share the same genes yet are unique and often hugely different. Generally, these differences do NOT arise from
genetic difference or genetic mutations - they arise from environmental influences, often minute and subtle - epigenetics. By definition, an
epigenetic system should be heritable, self-perpetuating, and reversible
(in response to environmental change).
Epigenetics is generally accepted as "resulting from external rather than genetic influences." Or more scientifically, as "the study of changes in
gene function that are mitotically and/or meiotically heritable and that do not entail a change in DNA sequence."
The cells in a multicellular organism have nominally identical DNA sequences (and therefore the same genetic instruction sets), yet maintain
different terminal phenotypes. This nongenetic cellular memory, which records developmental and environmental cues (and alternative cell states in
unicellular organisms), is the basis of epi-(above)–genetics.
The lack of identified genetic determinants that fully explain the heritability of complex traits, and the inability to pinpoint causative genetic
effects in some complex diseases, suggest possible epigenetic explanations for this missing information. This growing interest, along with the desire
to understand the “deprogramming” of differentiated cells into pluripotent/totipotent states, has led to “epigenetic” becoming shorthand for
many regulatory systems involving DNA methylation, histone modification, nucleosome location, or noncoding RNA. This is to be encouraged, but the
labeling of nongenetic systems as epigenetic by default has the potential to confuse (see the related video at
So what is epigenetics? An epigenetic system should be heritable, self-perpetuating, and
reversible (Bonasio et al., p. 612).
Epigenetics literally means "above" or "on top of" genetics. It refers to external
modifications to DNA that turn genes "on" or "off." These modifications do not change the DNA sequence, but instead, they affect how cells
It may be possible to pass down epigenetic changes to future generations if the changes occur in sperm or egg cells. Most epigenetic changes that
occur in sperm and egg cells get erased when the two combine to form a fertilized egg, in a process called "reprogramming." This reprogramming allows
the cells of the fetus to "start from scratch" and make their own epigenetic changes. But scientists think some of the epigenetic changes in parents'
sperm and egg cells may avoid the reprogramming process, and make it through to the next generation. If this is true, things like the food a person
eats before they conceive could affect their future child. However, this has not been proven in people.
RE: Epigenetics can override genetic programming, and change the protein that was programmed for production.
I agree. But the article in the OP seems to be saying that gene expression doesn't have much to do with it. It's all about, "how the cell
DNA is the "mechanism" for genetic activity and inheritance; the 2nd law of thermodynamics, and the environment in which the folding takes place are
the "mechanisms" for epigenetic activity and inheritance. Two difference processes with different mechanisms.
When a gene, a string of bases on the DNA molecule, is deployed, it is first transcribed and then translated into a peptide – a string of amino
acids. To give rise to biological properties it needs to "fold" into a protein.
This process consumes energy and is therefore governed by the 2nd law, but also by the environment in which the folding takes place. These two factors
mean that there is no causal relationship between the original gene coding sequence and the biological activity of the protein.
edit on 22/2/14 by soficrow because: oops
edit on 22/2/14 by soficrow because: format