I think all epigenetic modifications are non genetic and they occur due to action of cellular micro and macro environment. It may be possible that some epigenetic modifications under the control of non coding genes but yet they are not explored.

Hi!

Certainly nurture and environment play role in epigenetic inheritance.

Until Waddington explains the developmental pathways followed by cell how the external forces shape the fate of organism that how genes of an organism generate the phenotype; the visible characteristics of an organism resulting from the interaction between its genetic makeup and the environment it is believed that DNA the blueprint of organism’s life contains all instructions that need for development, survival, reproduction and stores the information. The word “canalisation” also coined by him. Ability of a population to produce the same phenotype regardless of variability of its environment or genotype.

There are many definitions for epigenetics. Robin Holliday defined epigenetics as "the study of the mechanisms of temporal and spatial control of gene activity during the development of complex organisms". Arthur Riggs and colleagues ,"the study of mitotically and/or mitotically heritable changes in gene function that cannot be explained by changes in DNA sequence”. Adrian Bird "the structural adaptation of chromosomal regions so as to register, signal or perpetuate altered activity states". In 2008, a unanimous definition, "stably heritable phenotype resulting from changes in a chromosome without alterations in the DNA sequence", was coined at a Cold Spring Harbor meeting.

As such there is no epigenome exists to store the epigenetic signals, still they inherit, epigenetic inheritance do not follow classical Mendelian laws. Interestingly epigenetic changes can be reversed. Though multicellular organisms have identical cells functionally and structurally they are different due to the differences in expression of genes during their cell division. These are not heritable, means they do not involve any changes in DNA sequence, we can mention that the chemistry of DNA alters to bring the epigenetic changes but not the sequence of DNA hence there is no changes in observed in DNA sequence. These changes or modifications occur typically in early life i.e. during cell division . “Imprinting” the only technique explain about epigenetic phenomenon. Best way to investigate gene expression of parent of origin. In genomic imprinting the expression of the gene depends on parent of origin whether paternal or maternal. It is called monoallelic expression.

The first recognized syndromes in humans are Prader-Willi syndrome and Angelman syndrome by Nicholls et al. in 1989. If the deletion of gene paternally inherits cause Prader-Willi syndrome. Otherwise deletion inherits maternally Angelman syndrome . Chromosome 15q11-13 alleles show difference whether inherited from mother or father

The mechanism involved in epigenetics are 1. DNA methylation; 2. Histone modification; 3. Chromatin structure; and 4. RNAs (RNA based mechanisms).

Probably the topic for future research, very interesting literature is available for reading.

This is a very interesting and salient topic. However, there is not real data to explain either side. However, in my opinion, certain selection factors would favor certain gene expressions, or pathways. Thus, certain pathways are ultimately adaptations as well.

Michael, you get vast literature. Go to either NCBI Pubmed or Google type the word "Genomic imprinting" or if you want to check in general type "Epigenetics".

I wonder to see the words "there is not real data to explain either side"

Jeff, that is an example, not an experiment. The extent to which adaptation affects the actually expression of genes is an opinion, unless you want to offer data or a survey of the literature base for epigenetic adaptation. Our understanding of either side is still limited.

From a genomic imprinting standpoint, the argument is quite limited. The extent of imprinted genes is quite limited; only 1 percent of genes are "imprinted" in humans. The full extent to which adaptation affects gene expression is still quite debatable

http://www.sciencedaily.com/releases/2007/11/071130075016.htm

Hi! I am not Jeff my name is Jetty Ramadevi.

Of course basing on examples only research go ahead why they are happening. So the researchers set experiments to find out reasons, right! Here Ishtiaq asked "To what extent our nurture and environment affects epigenetics? Are these epigenetic adaptations are inheritable?". As per the findings nurture and environment play crucial role in that so I mentioned right from the beginning they are inheritable but can not detect by DNA sequence could be detected by "imprinting". You too mentioned it is salient topic.

Genomic imprinting (Imprinted genes) was carried at a time in different laboratories McGrath and Solter and Surani and his colleagues’ in 1984. Direct evidence came from Surani et al.(1984). Yes the data available is limited for God's sake otherwise it would have been chaotic. At least we should realize now to protect environment and have good nurture habits for forth coming generation.

See the following "The Ghost in your Genes" very nice documentary

http://www.youtube.com/watch?v=dibpxvU4ml0

the following give some information of genes by species wise

http://www.geneimprint.com/site/genes-by-species

basic points about imprinting

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/I/Imprinting.html

Epigenetics vs Environment and Nutrition

http://learn.genetics.utah.edu/content/epigenetics/

Genomic imprinting gives an example of a phenomena where inherited traits violate Mendalian law of parental equivalence; however, questions may be asked to the extend to this phenomena occurs and gene expression is pre-determined or unit for creating evolutionary diversity.

Adaptation affecting Epigenetic process is counter intuitive for a biologist. Biological adaptation is typically viewed at the genomic level, with changes in allele frequency being an indication of evolution; not necessary changes in the pathways of a gene product.

However, very limited evidence indicates that marked gene expression, without changes in sequence variation, may allow for evolution to occur; the concept is pretty novel in evolutionary biology(attached is a recent article on the matter)

http://www.evolutionnews.org/2013/09/epigenetics_may076551.html

Interesting question.

Yes it is a fact that Epignetics violates Mendel's laws. We have been saying that the changes of imprinting are not stored or alter the DNA sequence; then arouse the question how they inherit? Still they inherit against Mendelian genetics as these changes occur in embryonic development where the chemistry of DNA is being altered rather than the sequence of DNA. Surprisingly “dominance” mentioned by Mendel either color or whatever one of the 7 characters he chosen to interpret laws of segregation and independent assortment, he mentioned one is either dominant or recessive over other. But did not tell from which parental part it is inheriting though he had done reciprocal crosses rather independent or influence of environment matters. Certainly we have to remember “law of acquired characters” proposed by Lamarck. Still puzzling question to scientific community.

Epigenetics does not violate Mendel’s laws; genomic imprinting is an exception to the overall principle.

Many genes are temporally silenced during Oogenesis and Spermatogenesis, however, after zygote formation the epigenetic markers are reprogrammed and zygote inherits 2 functional alleles. In the case of imprinted genes, these genes bypass reprogramming and remain not functional.

Like many biological phenomena, imprinting has its roots in evolution advantage. Evolutionary pressure favors, in certain circumstances, only the expression of certain genes that are necessary for producing offspring with the best chance of survival; most imprinted genes are involved in growth processes. Thus, in some circumstances, imprinted genes assure for healthier offspring.

Imprinting or genomic imprinting is an epigenetic phenomenon. May I know how you differentiate from each other?

As these changes occur during embryonic development epigenetic mark is added. In a polite way rather violation of Mendel's laws we can say epigenetically marked or tagged traits show non-Mendelian inheritance. Imprinted genes provide an example of epigenetic inheritance.

Evidence shows that most of them are associated with disease (1). So far growth related identified are IGF2, IGF2r, H19 where you observe abnormality in growth basing on inheritance either paternal or maternal.

As you mentioned it has "roots in evolution advantage", may be evolution is decent with modification (Darwin).

1. Transgenerational epigenetic inheritance in health and disease. Current Opinion in Genetics & Development 2008, 18:273–279.

Epigenetics is the study of gene expression.

Genomic imprinting is a epigenetic phenomena where the sex of the parent plays a role in inhibiting gene expression in certain genes.

It is generally regarded that genomic imprinting occurs because selection factors favor adaptability and that gene silencing curtails some of advantage.

There are many examples where imprinting genes leads to a defect, however, this does entail the full extent of the phenomena.

You agreed "genomic imprinting is a(n) epigenetic phenomena " that is fine.

Hello Mike,

This is a very pertinent question. Nurturing and environment plays a very important part in epigenetic alterations. As in, the folates are the special starter that is the base of methylation in the DNA as well as in the proteins. Folates come from rich protein diet and is comparatively low in the vegetables.

I work in the field of arsenic toxicity in West Bengal, India. Here, based on the family socioeconomic status I do encounter various epigenetic as well as health manifestations as the poor can't afford a high protein rich diet. So, from my hands on experience, one should always consider the environmental and socioeconomic aspects; diet while considering a epigenetic study.

Best,

Somnath.

Hi Ishtiaq, I just did a blog post on transgenerational epigenetic inheritance: http://episona.com/3-examples-transgenerational-epigenetic-inheritance/. My take is there is certainly evidence for heritability of these epigenetic changes; however, I think the extent of these is probably less broad than people are hoping for. My guess is that most epigenetic changes to the gametes are either erased during reprogramming or decrease the chances of a successful pregnancy if they aren't.