Beyond the Genetic Code

Written by Sophia Nguyen

For decades, biology taught a relatively simple narrative: DNA is destiny. An individual will inherit a fixed genetic code that determines health, behaviour, and disease risk. Yet, this explanation fails to account for a growing body of evidence showing that identical genetic sequences can produce dramatically different outcomes. If genes alone dictated biology, identical twins would develop in identical ways–but they do not.

To understand why this is, it is first necessary to understand what DNA does. DNA contains the instructions needed to build and maintain the human body. These instructions are organised into genes, which are specific sections of DNA located on chromosomes. Each gene carries the information needed to produce a particular protein. 

However, DNA only influences the body when it is actively used. Although every cell contains the full genetic code, most genes remain inactive most of the time. A gene must first be read by the cell and converted into a working product. This process begins with transcription. When a gene is switched on, the cell produces a temporary copy of its instructions in the form of messenger RNA (mRNA). mRNA carries this genetic message from the DNA in the nucleus to ribosomes in the cytoplasm, where proteins are assembled (“Transcription”). These proteins perform essential tasks throughout the body: regulating hormones, transmitting nerve signals, and controlling chemical reactions. 

Whether a gene is expressed determines whether a specific protein is produced, how much of it is made, and when it is used. 

Epigenetic Control of Gene Activity

So, although every cell contains the same DNA, not every gene is expressed in the same way. Epigenetics offers an explanation as to why this is. It refers to changes, caused by the environment, that affect how our genes are expressed, while the epigenome is the collection of chemical marks that sit on DNA and histones. Unlike the genome, which is fixed at birth, the epigenome is everchanging. It is shaped by countless forces, some of which begin exerting their influence before an individual is even born. For example,  a mother’s diet during pregnancy (Cleveland Clinic). Two of the most important epigenetic mechanisms are DNA methylation and histone modification.

DNA methylation involves attaching a chemical group, called a methyl group, to specific locations on the DNA molecule. This does not change the genetic code itself; instead, it affects whether or not a gene can be read. When methyl groups accumulate near the start of a gene, they interfere with the cell’s ability to access that gene, effectively reducing or preventing its activity (Beech). One way to visualise this is as a piece of tape placed over a line in a paragraph. The words are still there, but they are harder to read. In cells, DNA methylation helps ensure that genes are turned off when they are not needed.

Histone modification regulates gene expression differently. DNA is tightly wrapped around proteins called histones, forming a structure known as chromatin. The way DNA is wrapped determines how accessible it is. Chemical changes to histones can either loosen or tighten this packaging. When histones are modified in a way that loosens their grip on DNA, genes become easier to access and more likely to be expressed. When the DNA is packed tightly, gene expression is reduced (“Genetics, Epigenetic Mechanism - StatPearls - NCBI Bookshelf”). Together, DNA methylation and histone modification act as a regulatory system that allows cells to respond to their environment.

Why Epigenetics Matters for Health and Disease

Epigenetics reveals how environmental conditions influence gene expression without altering the DNA sequence itself. Understanding epigenetics reframes biology from something fixed and predetermined into something responsive and dynamic. It shows that health is shaped not only by the genes we inherit, but by how our environment influences the way those genes are used. As research continues to expand, epigenetics transforms modern medicine by suggesting that biology is far more adaptable than once believed.

However, epigenetics remains an active and rapidly developing field of study. Ongoing research suggests that epigenetic changes are involved in ageing, disorders affecting the brain, and the development of cancer, but much is still not fully understood. There is no single blueprint for improving the epigenome since the effects of environmental influences can vary between individuals. Scientists believe that a positive lifestyle–such as a balanced diet, low stress, and supportive social relationships–can promote gene expression patterns that support healthy brain development and immune function (Cleveland Clinic). Speaking with a healthcare provider can also help clarify how your unique genetic makeup interacts with your environment. Ultimately, epigenetics offers the reminder that our genes are not our destiny and underscores how much we are still learning about the intricate relationship between our biology and the world around us.

References

Beech, Tim. “What is DNA methylation? | DNA Methylation Overview.” biomodal, https://biomodal.com/blog/the-fascinating-world-of-dna-methylation/. Accessed 13 February 2026.

Cleveland Clinic. “Epigenetics.” my.clevelandclinic, https://my.clevelandclinic.org/health/articles/epigenetics.

“Genetics, Epigenetic Mechanism - StatPearls - NCBI Bookshelf.” NCBI, https://www.ncbi.nlm.nih.gov/books/NBK532999/. Accessed 13 February 2026.

“Transcription.” National Human Genome Research Institute (NHGRI), https://www.genome.gov/genetics-glossary/Transcription. Accessed 13 February 2026.