Genes are bundles of DNA that exist in your cells that affect how you look, grow, and age. Since the human genome was fully decoded in the 1990s, researchers have been working to figure out what all the genes do. Height is one example of a trait that has been investigated.
Although height is an inherited trait, it is impossible to pin it down to just one gene. In fact, over 700 different genes have been found to contribute some small amount to your adult height. However, all of these genes together only account for about 20% of how tall you are. Therefore, there must be some undiscovered set of genes, or unknown effects of known genes, that contribute largely to your height. But what are these genes? What is it in our genetic encoding that actually determines how tall we grow?
An international team of over 300 scientists worked together to find out. Their work was recently published in the journal Nature, explaining in detail their attempts to search for rare genes that have a big impact on height, rather than searching for common genes that so far only showed a small effect. One of their hypotheses was that rare genes have a bigger effect on height than common genes. If their hypothesis is supported, this could go a long way toward helping us understand why we are born as tall, or as short, as we are.
Recent advances in genetics technology allows researchers to compare a greater number of traits and genes at a time. This enhanced technology allows researchers to find more relationships between genes and traits, and thus see which traits are impacted by which genes. However, before they could begin searching for multiple genes at once, they tested their methods by searching for one known, common height gene among their 458,927 study participants. They did this to demonstrate that their methods worked, by finding an already known relationship between that height gene and the few millimeters it provided. They did this search by looking for the gene in the study participants, and verifying that on average, the participants with this gene, were indeed a few millimeters taller!
After their single-gene study, the researchers did the same test again, this time analysing a different set of people. They had to do this ensure their initial finding was not just coincidental. They did see quite clearly in the evidence, that those who did not have this gene, were indeed shorter on average, than those with this gene. This means that the less often a gene occurs, the greater the impact it has on height! These results validated the researchers’ hypothesis.
In part of their study, they dug through large data banks searching for rare genes which might possibly contribute to height. Of the 83 genes rare genes they found, they pinpointed ten genes that affect height by 27%, three of which had never before been thought to contribute to human height!
But, how do these genes actually determine height? There are an extraordinary number of biochemical reactions that contribute to height, such those that control how a baby grows in it’s mother’s womb, how cartilage forms, and how bone growth is regulated. Our genes provide the instructions for how our cells should turn these processes on or off during the course of a person’s life.
There is still more work to be done. We cannot yet look at a person’s genetic makeup and determine precisely how tall they will be. However, we can comparatively say if someone may be taller or shorter with a little bit more confidence now..
The major finding, that rare genes may have larger effects than common genes, even in complex systems (such as height) that have numerous contributing factors, will help other researchers study diseases. Chronic diseases with genetic roots often are controlled by many genes, and looking for the rare ones may lead us to be better able to predict our risk for heart disease, cancer, autoimmune diseases, and more.
So next time you find yourself wondering how you got to be the height that you are, keep in mind — it’s complicated!