What is epigenetics? An easier to understand definition with illustration

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3959995/
A really good article with excellent diagram illustrating how epigenetics works. Published in 2009.
Spend some time with the illustration first before reading the article. Click on the illustration and it gets much larger.
Excerpt from the webpage:
"Abstract
A recent meeting (December 2008) regarding chromatin-based epigenetics was hosted by the Banbury Conference Center and Cold Spring Harbor Laboratory. The intent was to discuss aspects of epigenetic control of genomic function, and to arrive at a consensus definition of "epigenetics" to be considered by the broader community. It was evident that multiple mechanistic steps lead to the stable heritance of the epigenetic phenotype. Below we provide our view and interpretation of the proceedings at the meeting."

definitions:
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Epigenetics - in a broad sense, is a bridge between genotype and phenotype—a phenomenon that changes the final outcome of a locus or chromosome without changing the underlying DNA sequence.
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chromatin: Mass of genetic material composed of DNA and proteins that condense to form chromosomes during eukaryotic cell division. Chromatin is located in the nucleus of a cell.
A complex of nucleic acids and proteins, primarily histones, in the cell nucleus that stains readily with basic dyes and condenses to form chromosomes during cell division.
Only recently, the role of DNA packaging into chromatin emerged as one of the major contributors to the modularity and dynamics of the genome.

At its most basic level, chromatin functions to ensure the proper organization, storage and readout of genetic information with remarkable spatial and temporal precision during processes of cellular differentiation and organismal development
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milieu
1. The totality of one's surroundings; an environment.
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An epigenetic trait is a stably heritable phenotype resulting from changes in a chromosome without alterations in the DNA sequence.”
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genomics - the branch of genetics that studies organisms in terms of their genomes (their full DNA sequences)
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functional genomics - the branch of genomics that determines the biological function of the genes and their products
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Phenotype - The physical appearance of an organism as distinguished from its genetic makeup ( Genotype). The phenotype of an organism depends
on which genes are dominant and on the interaction between genes and environment
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“Epigenator”-a signal which emanates from the environment and triggers an intracellular pathway. ( step one)
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“Epigenetic Initiator”- a signal which responds to the Epigenator and is necessary to define the precise location of the epigenetic chromatin environment. ( step two)
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“Epigenetic Maintainer”- a signal which sustains the chromatin environment in the first and subsequent generations. ( step three)
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Cell specialization, also known as cell differentiation : the process by which generic cells change into specific cells meant to do certain tasks within the body. Cell specialization is most important in the development of embryos.
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eukaryote : ( has cells with a nucleus) a creature in one of these 5 supergroups:
Archaeplastida (or Primoplantae): Land plants, green algae, red algae, and glaucophytes
SAR supergroup : Stramenopiles (brown algae, diatoms, etc.), Alveolata, and Rhizaria (Foraminifera,
Radiolaria, and various other amoeboid protozoa).
Excavata : Various flagellate protozoa
Amoebozoa : Most lobose amoeboids and slime molds
Opisthokonta : Animals, fungi, choanoflagellates, etc.
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epigenetic landscape:
Waddington's Classical Epigenetic Landscape
In 1957, Conrad Waddington proposed the concept of an epigenetic landscape to represent the process of cellular decision-making during development. At various points in this dynamic visual metaphor, the cell (represented by a ball) can take specific permitted trajectories, leading to different outcomes or cell fates.
See this excellent short article for illustration of this definition: http://www.sciencedirect.com/science/article/pii/S0092867407001869
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Terminally Differentiated Cells - Cells most distal to the stem cell, being differentiated to perform a specific function, but having permanently lost the ability to divide
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And how about this statement! : In addition, the ability to epigenetically reprogram differentiated cells is becoming of medical importance.
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Ok , now if that didn't get you excited, take a look at this:

NUTRIGENOMICS FOR POULTRY-NEW TOOLS FOR MAXIMIZING PERFORMANCE ( 24 pages long)
Christopher M. Ashwell
Department of Poultry Science, North Carolina State University
Campus Box 7608, Raleigh, NC 27695
http://www.thepoultryfederation.com...Chris Ashwell - Nurtigenomics for Poultry.pdf
Excerpt ( bold is mine):
"Broilers fed a diet moderately deficient in P and Ca from hatch to 18 d demonstrated ability to adapt to the deficiency, which is shown in the increased total P and Ca ileal absorption, the increased PP disappearance, compensatory growth, and compensatory improvement in bone parameters including tibia ash, tibia and shank bone mineral density and bone mineral content in a later growth phase (18 to 32 d) (Yan et al, 2005). However, practical application of the adaptation rule requires more studies to further fine tune the degree, timing, and length of the restriction with the aim of achieving minimal changes in bone, associated with no changes in performance, since bone characteristics are one of the primary determinant of downgrades of poultry products in the processing plants. These published data indicate that in birds during the period immediately post hatch there is a phenomenon occurring that permanently alters the bird’s response to its environment. This adaptation or conditioning, which-ever term you choose to use, is a real observable fact for which no underlying mechanism has been previously proposed. Is this new form of genetic effect epigenetic in nature? Studies are ongoing to determine if the mechanism of persistent responses of gene expression to stimuli are epigenetic in nature. If epigenetic regulation is involved in dietary conditioning the opportunities for nutrition to impact both the animal and its offspring are almost limitless. "
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Page 10 and 11 of 24 on the topic of: "The greatest potential to elicit an epigenetic response in progeny is likely by manipulating the diet of the maternal parent. "
Page 11 topic perinatal nutrition : : "The nutrients deposited into the egg by the hen are the only source of nutrients available to the embryo, and this may be the last chemical means by which the hen may transfer an epigenetic message to its offspring. "
Page 18 and 19 , part of the summary : "The data included in this summary along with other preliminary data demonstrating long term effects on performance and gene expression as a result of nutritional manipulation in the chick are strong evidence for the role of epigenetics in the regulation of these phenomena. Further work must be conducted to elucidate the specifics of neonatal programming in the chicken, the extent of its effects on DNA methylation of the NaPcoT as well as other genes. Demonstrating these epigenetic effects in the chicken will provide both a significant contribution the understanding of the regulation of genomes, particularly in oviparous species but also provide a potential mechanism for improving performance and the economics of poultry production.
This adaptation or conditioning, which-ever term you choose to use, is a real observable fact for which no underlying mechanism has been previously proposed. Is this new form of genetic effect epigenetic in nature? Studies are ongoing to determine if the mechanism of persistent responses of gene expression to stimuli are epigenetic in nature. If epigenetic regulation is involved in dietary conditioning the opportunities for nutrition to impact both the animal and its offspring are almost limitless. "

Hi,
I am currently researching the epigenetic effects from nutrigenomics on the chick embryo and neonate chick
( hatch to 2 weeks old) . With a view to determining a better way to get chicks started off in life for a better overall lifetime. I will be uploading and organizing my research on this thread. The commercial broiler and layer industries have amazing research and success going on in these areas. Work which I know can be simplified to work for the backyard breeder.
This thread will encompass new ways of feeding dry feed with supplements. It is not a fermented feed thread and will not discuss it. We all have our own ways of feeding our birds. However, wet feed is not an object of my research and not a consideration at this time.
Thank you for reading,
Karen

I joined this forum just to say THANK YOU for sharing what you know about this subject! I do not have a scientific mind (more of an artist) but the epigenetic effect is fascinating, and I really want to know more about it!

If you have ever seen the difference between children raised in Vietnam and Vietnamese children that are raised in the USA, the children raised in USA are larger and appear to be more healthy than the children raised in Vietnam. The children in vietnam may be genetically programmed to be larger- due to poor nutrition and lack of health care the children do not obtain a larger status.

Subscribing!!!