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In an article on biomarkers of child abuse, the author referred to an "epigenetic mark on a person's DNA". It's a popular science article, so the language may reflect a combination of the journalist's scientific competency and his or her desire to communicate complex topics efficiently to a lay audience. Is that an example of such language?

My understanding was that anything in the realm of "epigenetics" is happening to something other than DNA. Is it technically correct to refer to an "epigenetic mark on a person's DNA"? Correct enough? Only potentially misleading? I'm trying to wrap my head around the whole epigenetics concept.

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We may restrict your definition of epigenetics as heritable changes in an organism's phenotype that occur without a change in the sequence of DNA bases. That is, changes to the DNA molecule itself is permitted, as long as the sequence of ATCGs are not affected.

In this sense, it would not be wrong to refer to an "epigenetic mark on a person's DNA". For example, a mechanism of epigenetics that does directly change the DNA molecule would be something like DNA methylation.

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  • $\begingroup$ Then the article is incorrect, because it does not establish that the chemical modification to the DNA has been inherited or will be inherited, regardless of whether it has any function, which clearly has not been established. $\endgroup$ – David Oct 8 '18 at 21:26
  • $\begingroup$ @David I don't see any part of this answer that demonstrates that the article is incorrect, again given the interpretation for "inheritance" in epigenetics, which does not necessarily refer to inherited by the offspring (per our comment conversation on your answer and the final paragraph of your answer). $\endgroup$ – Bryan Krause♦ Oct 8 '18 at 22:16
  • $\begingroup$ @BryanKrause — It would seems that an extensive answer — considering and distinguishing the different definitions or interpretations of the term is needed on SEBiology to deal with epigenetics. I'm not sure this is the best question to use, as ultimately the poster's concern seems to be more at the level of base methylation v. histone modification as epigenetic. $\endgroup$ – David Oct 9 '18 at 15:46
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It all depends on your definition of epigenetic. The one assumed by @ning, that appears to fit the case, is that cited in the Wikipedia article on the topic is:

“Epigenetics is the study of heritable phenotype changes that do not involve alterations in the DNA sequence”

Methylation is a change in DNA that does not involve altertion in the DNA sequence. For observations of such marks to be epigenetic it needs to be proved that they also:

  1. Have a phenotype. In this case the association of the methylation with behavioural changes resulting from child abuse is not asserted or demonstrated.
  2. Be heritable. This is also not asserted or demonstrated in the article.

I am unaware of any circumstance in humans in which these three conditions have been satisfied.

Epigenetics without inheritance

I think the confusion and pseudo-science associated with this topic arises from the fact that DNA methylation can play a role in differentiation of cells during the lifetime of higher organisms, which has also been termed epigentic. This has been confabulated with experiments on inheritance of methylation patterns in bacteria. A resulting epiphenomenon has been a revival of credence in the criminal fraud of Trofim Lysenko.

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    $\begingroup$ In literature on epigenetics it is common to take the "heritable phenotype" in your first definition to include inheritance within cell lines in an individual, rather than the more common use of the term to mean across generations, though clearly the article in the OP was referring to generational changes. I'd say this is especially true in 'epigenetic' research into cancer where the term really just means "long-lasting changes in gene expression that are carried to daughter cells." $\endgroup$ – Bryan Krause♦ Oct 8 '18 at 21:51
  • $\begingroup$ @BryanKrause — Agreed, as I hope my rider made clear. But the abuse of the real science by gutter journalists and people with a political agenda really annoys me. $\endgroup$ – David Oct 8 '18 at 21:55
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    $\begingroup$ Understood, and I know you have been an opponent of (intergenerational) epigenetic studies on previous questions here. I have to say though, although imperfect, I thought this article was actually a very fair assessment for a more pop science article, have you actually read it? It makes the controversy pretty clear and identifies accurately the current state of research: someone is reporting some methylation changes in sperm and are uncertain at this point if those make it through to offspring. $\endgroup$ – Bryan Krause♦ Oct 8 '18 at 22:01
  • $\begingroup$ I'm not sure you mean confabulate. Autocorrect? $\endgroup$ – De Novo Oct 9 '18 at 4:18
  • $\begingroup$ The word suddenly came to mind, so I checked with Merriam Webster who give one definition as "to fill in gaps in memory by fabrication". Seemed quite a good fit. $\endgroup$ – David Oct 9 '18 at 15:40

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