People with Huntington, Marfan syndrome, cystic fibrosis or anaemia falciforme have one thing in common: a single gene is the cause of their suffering. Obviously the gene is a different one for each of them, but they are all “monogenic” diseases precisely because they are caused by one gene only.
In the first two cases, receiving only one copy of the mutated gene is enough to suffer the disease: they are monogenic “dominant” diseases. Cystic fibrosis and anaemia, on the other hand, are “recessive”, and it is necessary to receive the mutated gene both from the mother and the father.
In most cases, however, things are not that easy. Most of the genetic diseases are caused by errors in several genes at the same time. Furthermore, there isn’t always a causal relationship between having specific genes mutated and suffering a disease, but the environment, diet and life style have also a lot of influence. This is why talking about these “complex” diseases, such as high blood pressure, diabetes or even cancer, the experts say that a person has a certain “predisposition” to develop a disease. This means that he or she has mutations in some genes that will make the disease develop, but only if one day they are joined by mutations in other genes and specific environmental conditions.
Complex diseases are the consequence of a combination of several genes and the environment. A higher predisposition to develop one of these diseases doesn’t mean they are going to appear for sure.
A higher predisposition to develop one of these diseases doesn’t mean they are going to appear for sure. This complexity and our ignorance of all the factors involved mean that making predictions based only on genetics is very difficult. So, while thousands of geneticists at the Barcelona Biomedical Research Park (PRBB) and all over the world keep on studying the bases of genetic diseases, we all have to try to control the only part of the equation that we can so far modify and have a healthy and equilibrated life style living in a non-polluted environment.
