The human body is far more complicated than our relatively small number of genes suggests – now scientists have shed more light on why this might be the case.

Studies suggest that one reason why humans are such complex beings – despite having a similar number of genes to a fruit fly – could be down to molecules called RNA, which normally interact with genes to produce the proteins that make up our bodies.

The team at the University of Edinburgh suggests that the way a certain type of RNA interacts with genes allows regulation of how often and how much protein is created, so that protein production is more complex than in simpler organisms.

Normally, information held in genes is copied into RNA, which is then used to construct the proteins that make up our bodies. However, the Edinburgh study has shown that not all RNA is involved in this process and some RNA molecules can instead change the amount of protein that these genes produce.

The Edinburgh team studied yeast and found that a particular type of yeast RNA appears to have evolved to fine-tune a set of genes, adding a layer of complexity that better allows the yeast to adapt to a changing environment. As yeast is biologically similar to plants and animals, including humans, it is likely that we have RNA that carries out a similar function.

Professor David Tollervey, of the School of Biological Sciences, who carried out the research, said: “Humans have around 24,000 genes, fewer than many plants and not many more than simple worms. But, of course, we are actually much more complex than this comparison suggests. Our findings suggest that RNA plays a role in adding layers of complexity to the regulation of expression of our genes.”

The study, carried out with UCLA, was published in the journal Molecular Cell.