We explain what lies beyond DNA.
Despite criticism from parts of his evolutionary theory, Jean-Baptiste Lamarckpostulated that changes in species derive from the activity of animals during their lifetime (for example, if a giraffe stretches its neck a lot, it will grow its neck and its offspring will have a longer neck).
While it’s a flawed and simplistic view of evolution, it has a lesson we’ve recovered over time: What we do during our lifetime affects us, and can affect our descendants. This happens through epigenetics, an extra system of genetic control that changes throughout our lives.
What is epigenetics?
We could define epigenetics as the branch of science that studies thechanges that occur in DNA without affecting the DNA sequence. That is, it studies the processes that change DNA, its function and its expression, as long as these do not affect the “message” that DNA contains encoded in its base pairs.
Epigenetics was revolutionary: Discovering that there were indeed characteristics at the genetic level that vary throughout our lives, which are also capable of being transmitted to offspring in certain caseswent against certain axiomsthat were considered in the scientific community.
Over time it has been seen that epigenetic processes are related to multiple diseases, such as cancer, Prader-Willi syndrome, diabetes, or even psychological disorders, such as depression, anxiety or insomnia.
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1. How it controls DNA
At the molecular level, epigenetic changes can be explained in a simple way. If our DNA were a book that cells read to know what they have to do, epigenetic changes would be processes that would paste or separate the pages of the book, making it difficult or easier to read certain passages.
Stated more technically, epigenetic changes result in changes at the level of gene expression: The parts of the genome that are “more difficult to read” cannot be freely transcribed into proteins, decreasing the so-called “expression” of the zone of the DNA that is being regulated.
This occurs through different mechanisms. The most studied currently is probably methylation, the conjugation of small molecules to specific parts of DNA, such as CpG dimers, which are nothing more than Cytosine and Guanine placed one after the other, which have a tendency to be methylated being in this position.
2. What are CpG islands?
CpG islands are distributed in a curious way in our DNA. They are quite rare throughout the genome, but when we study an area of our DNA where many genes are encoded, we will see that these dimers are much more frequent than usual. Most of the CpG islands are found in promoters , parts of the DNA related to the increased expression of one or more adjacent genes.
The high methylation of CpG islands near the promoters of a gene makes it more difficult to transcribe them, the process of passing from RNA to DNA. In some cases, the methylations simply “bother” some protein necessary for the action of the promoter, but in others, the methylation causes a small “condensation” of the DNA fiber.
During this process, the DNA fiber changes from being euchromatin, a state in which DNA is easily transcribable, to being heterochromatin , a more “coiled” and tight type of DNA, whose transcription will be less frequent, or not occur until reverse this methylation. This occurs thanks to the action of proteins that act on these highly methylated areas.
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Is epigenetics heritable?
Epigenetic marks can be acquired during the course of life . These changes occur in response to certain environmental factors, such as intense stress, famine seasons, extreme temperatures… There is also a certain epigenetic marking dependent on habits such as smoking, or also related to aging. These epigenetic marks have different magnitude, effects and longevity.
When embryogenesis occurs (the process by which a new being is formed from gametes) a curious process of erasing the epigenetic marks of the parents occurs before the new life begins to form. Due to this, there was initially the idea that epigenetics should not have a heritable component.
Today, thanks to a multitude of experiments, we know that epigenetics does have a certain heritable factor , and that part of the epigenetic marks that we acquire during our lives can be passed on to our offspring. This was observed, for example, in the pups of mice that had suffered intense stress during their lives, such as that which occurs when they are separated from their mothers too early.
The epigenetic marks that the “stressed” mice developed were passed on to their offspring, which repeated behaviors similar to those of their parents, such as greater susceptibility to stress or greater hostility in the face of unexpected scenarios.
Why is it important to study it?
Science is moving in multiple directions at once . Sometimes, science is necessary that does not obtain direct applicability in the short term, since it can be the basis for future experimentation, where the technological level allows knowledge to be better explored. We know this as basic science and much of the scientific progress in all fields is based on it.
Epigenetics, however, is far from being a merely theoretical or difficult to apply science . Epigenetic analyzes can be carried out today, and the information that we can extract from them can open many doors for us, especially in the field of health.
Epigenetics is studied today in relation to fields such as:
- The mechanisms of aging
- Cancer
- psychiatric disorders
- The evolution and adaptation of species
- The alergies
- degenerative diseases such as Alzheimer’s
- Cardiovascular diseases
Among many others, sinceepigenetics is not a process that affects only human beings. In fact, the epigenetic patterns of each species can vary quite a bit between them, suggesting different uses of this “living technology” of DNA control. It is a living and very interesting field in the world of genetics.
References
- Nestler E. J. (2014). Epigenetic mechanisms of depression. JAMA psychiatry, 71(4), 454–456. doi:10.1001/jamapsychiatry.2013.4291.
- Trerotola, M., Relli, V., Simeone, P., & Alberti, S. (2015). Epigenetic inheritance and the missing heritability. Human genomics, 9(1), 17. doi:10.1186/s40246-015-0041-3.
- Seisenberger, S., Peat, J. R., Hore, T. A., Santos, F., Dean, W., & Reik, W. (2013). Reprogramming DNA methylation in the mammalian life cycle: building and breaking epigenetic barriers. Philosophical transactions of the Royal Society of London. Series B, Biological sciences, 368(1609), 20110330. doi:10.1098/rstb.2011.0330.
To the classic question “what do you do?” I always answer “basically I am a psychologist”. In fact, my academic training has revolved around the psychology of development, education and community, a field of study influenced my volunteer activities, as well as my first work experiences in personal services.