Inside the cells of our bodies are chemical structures (called DNA) that carry our genetic information. Sections of DNA, that we call ‘genes’ act as instructions for how our body should grow, develop, and function.

We are estimated to have around 20,000 genes. Variations in our genes (like a spelling variation in an instruction) are common, and make us unique. However, sometimes, a variation can stop the gene functioning properly.

Monogenic refers to traits where variations in just one of our ~20,000 genes (mono=one, and genic=referring to genes) is sufficient to cause a person to express the trait(s) or not. These traits can be harmless, like freckles, or they can cause genetic conditions like cystic fibrosis or Huntington disease. The genes for these conditions were identified by studying the genetic information of many people in many families with the condition. For people with rare genetic conditions who might be the only person in their family, or the only family in their community, finding the one gene out of around 20,000 can be especially challenging.