By Francesca Ceroni

Just like computers need a program to perform a specific task, so do cells that need DNA to perform specific functions. 

DNA is a molecule stored within all cells, from simpler bacteria to more complex mammalian cells that make up our body. DNA carries the instructions (genes) the cells need to produce proteins, molecules used by the cells for growth, movement and interaction with other cells. For proteins to be produced, genes need to be read by the cell, exactly as a computer does with program instructions. The reading of genes is possible because DNA sequences placed near the genes (promoters) act as switches that the cells can turn on and off to access the genes and produce specific amounts of proteins when needed. 

Biological engineers at first thought that DNA was an inert molecule and that each of its parts, like promoters and genes, acted independently and could therefore be moved from one location to another within the DNA without changing its behaviour, simply with a “plug-and-play” approach.

However, DNA parts have shown not to function in isolation but to “influence” each other and change their behaviour depending on the DNA sequences present at their sides. In bacteria, for example, promoters behave differently when placed near one gene or another, leading to the production of more or less protein depending on the promoter-gene pair.

This phenomenon is called the context dependency of the functionality of DNA parts and reminds us of the emerging properties found everywhere in nature, from biological systems to chemical elements: there is always what we can call a relational side to biological processes for which the interaction between two or more elements gives rise to properties specific to that ensemble, which is difficult to predict and not found elsewhere.