What Is Epigenetics?

Epigenetics is the study of all the genetic changes that occur in the organism without the need to modify the very nature of its DNA.

Written and verified by el biólogo Samuel Antonio Sánchez Amador.

Last update: 30 March, 2023

Epigenetics is a term used to refer to the study of the mechanisms that regulate gene expression without a change in the individual’s DNA sequence. In other words, this discipline tries to describe how environmental and extrinsic variables modify the phenotype.

Previously, it was believed that DNA was constant throughout an individual’s life, that is, that it was invariably expressed over time and only changed through mutation. This idea is increasingly being challenged. If you want to know more about epigenetics and learn about the world of genes, don’t miss this article!

Initial terminology

To start with, we think that it’s useful to include a small glossary that includes various terms related to DNA and genes. If you spend a couple of minutes trying to understand these concepts, then you’ll find it easier to understand the rest of the article.

Here are the most important ones:

• DNA: Deoxyribonucleic acid is a biomolecule made up of a double chain that contains the genetic information of living beings. All the instructions for building proteins in the body are encoded in the cell’s DNA.
• Bases/nucleotides: The basic unit of DNA is the nucleotide, which joins with others forming long chains to give rise to DNA and RNA. Each nucleotide contains a nitrogenous base that gives it its name: adenine (A), guanine (G), cytosine (C), thymine (T) and uracil (U).
• Gene: The basic physical information unit of heredity. Genes are arranged, one after the other, on structures called chromosomes. Only one segment of each chromosome corresponds to a specific gene.
• Chromosome: A long strand of DNA that contains genetic information. Chromosomes reside in the nucleus of all the body’s cells.
• Chromatin: The proteins and other materials that make up the chromosomes along with DNA.
• Genotype: The set of genes and genetic information that make up an individual of any species.
• Phenotype: The set of observable characteristics that an individual shows as a result of the interaction between its genotype and the environment.
• Exon: A gene’s DNA region that codes for a part of the protein. The exon is sandwiched between non-coding sequences or introns.
• Intron: A non-coding sequence of DNA that separates two exons.

Epigenetics and the human genome

The human genome project, launched in the 1980s and completed in 2003, reported a series of surprising data regarding our genetics as a species. Let’s take a look at some:

• The human genome contains about 20,000-25,000 genes. This translates to about 3.2 billion base pairs of DNA.
• The density of genes in our genome is low, as they only represent 1.5% of all genetic information. 70% is comprised of extragenic DNA and 30% is related to genes.
• Until recently, 75% of human DNA was considered junk DNA (introns). This means that it doesn’t code for proteins.

It’s this last concept that epigenetics tries to combat. As reported sources indicate, the supposed junk DNA is essential for the regulation of gene expression, that is, when a gene produces a protein or stops doing so.

The new concept of the chromosome

Thanks to new studies in terms of epigenetics, the concept of the chromosome has changed. Now the chromosomes are divided into 3 layers:

1. Protein-coding genes: The sole repositories of heredity.
2. Non-coding genes: Contrary to what was believed, they play a very important role. They’re essential for heredity and for the development of diseases and give rise to active strands of RNA, which alter the behavior of the encoding genes.
3. The epigenetic information layer: This is an important area that influences development, growth, aging, and cancer, among many other things. It doesn’t alter the DNA sequence as a mutation would, but it does either induce or inhibit its expression.

Epigenetics: changes in genes without the need for mutations

Epigenetics, according to the National Human Genome Research Institute (NIH), is an emerging field of science that studies heritable changes caused by turning genes on and off without changing the underlying DNA sequence of the organism. This can be achieved through various mechanisms.

1. DNA methylation

This is a process by which, as its name suggests, methyl groups are added to the DNA molecule. In these cases, the chromatin condenses, making the genetic information inaccessible. Roughly speaking, genes that code for proteins can’t be transcribed and proteins aren’t formed.

DNA methylation is essential for signaling which genes should be turned on or off definitively in certain developmental processes. This is carried out by enzymes, some of which are considered heritable.

2. Histone modification or epigenetic marks

Histones are the chromatin-forming proteins described above, along with DNA. Covalent histone modifications can be produced by different processes: phosphorylation, methylation, acetylation, and others.

Informative portals indicate that the premise is similar to the previous case. They inhibit or enhance the transcription of certain genes. These modifications are reversible, which means that there are enzymes responsible for undoing these changes.

3. ATP-dependent chromatin remodeling

Chromatin can be modified in a remodeling process dependent on ATP, a charged energy molecule. To summarize, we can say that this process allows movements, sliding, and unwinding of chromatin and histones. Thus, segments of DNA remain free and these will be transcribed into proteins.

The use of epigenetics in medicine

According to scientific information portals such as Euroespes Health, epigenetics may be the answer to many pathologies, but further study is needed. Here are some examples of its uses in medicine:

• Global DNA methylation: In cancer and metastatic processes, global methylation occurs at lower-than-expected levels. In this way, the study of methylation levels could give information about a pathology before it worsens.
• Methylation of individual genes: Some diseases are characterized by the altered rate of methylation in some important genes. Describing these atypical methylation rates can lead to an early diagnosis.
• Gene expression: The expression of certain genes can vary in some pathologies. Learning about epigenetics could mean that, in the future, these changes could be reversed to seek patient recovery.

Of course, all these uses are extremely promising and, although it may not seem so, some of the epigenetic markers have already been approved by the European Union and the United States Food and Drug Administration (FDA) for the early detection of certain types of cancer. The future of epigenetics is bright.

As you may have seen, epigenetics has come to challenge established dogmas. Contrary to what was believed, much of this junk DNA seems to be essential when it comes to activating or inactivating genes, which causes pathologies and other physiological events.

For this reason, the study of epigenetics is promising in the realm of science. Understanding how gene regulation affects the person’s phenotypic expression may be the first step to addressing multiple pathologies that doctors haven’t been able to treat using traditional means.