You all have the gene for breast cancer. You also have the cystic fibrosis gene, and the Huntington’s disease gene, and the genes for every other genetic disease. Don’t worry – every one of us has all of these genes. What people really mean when they say that someone “has the gene for a disease” is that the gene is not working properly in them and this has led to the disease.
Genes are the body’s instruction manual
We have 20,000 genes that provide the instructions for making the proteins used to build and control our bodies. The genes function in many different ways so that our brain, heart, muscles and all our cells perform complex actions flawlessly, every second of every day. There are no genes that exist to cause disease.
Genetic diseases occur when genes don’t work as they were meant to
Genetic diseases happen either because the gene is not working or not working well enough, or because the gene is working too well, or at the wrong time, or in the wrong place. Usually a change in the DNA code of the gene causes the problem. We have two copies of every gene so there is a back-up if one is not working as it should. Sometimes malfunction of one copy of the gene is sufficient to cause health problems, for example if one copy of BRCA1 isn’t working it causes an increased risk of cancer. Sometimes both copies of the gene have to malfunction for the disease to occur, for example in cystic fibrosis.
What is the problem in saying ‘have the gene for?’
Does it matter if people say they “have the gene for” when what they mean is that their gene isn’t working properly? In casual conversation, people will get the gist of what they mean.
But once you want to talk about genetics in more detail, the phrase “you have the gene for” quickly becomes a problem. It evokes an idea of a gene as something that shouldn’t be there, as something that is bad for you, something to be feared, something that you don’t want, that you don’t want to pass on to your children. This can make it more complicated to talk about details such as the likely significance of genetic variants.
Why do people say ‘have the gene for’?
Historically, we were talking about phenotypes and heredity long before we knew what genes were and how they worked. Mendel’s 19th century experiments showed there was a yet unknown heritable factor that determined the chance of a pea plant having certain features: A different colour flower, or a different shaped seed. But Mendel didn’t know about genes. The phrase “gene”, to describe this type of hereditary factor wasn’t introduced until the early 20th century. A few decades after that we learned that genes were made of DNA, but it wasn’t until the 21st century, that we discovered how many genes there are in the human genome. And the story didn’t end there: we still don’t know the function of every gene.
Many genes were first discovered because of links to disease
This brings me to another reason for the persistence of the phrase “the gene for the disease”. Many genes were first discovered because they are related to a disease. It was the search for the cause of the disease that led to the gene and so the first and sometimes only thing that was known about the gene was that changes in the DNA code of the gene causes medical problems. The name and symbol for the gene reflected this.
For example the BRCA1 gene was so named because the gene was first identified through the study of breast cancer families who all had mutations in a specific region of DNA on chromosome 17. The region was shown to have the characteristics of a gene, but the function of the gene was not yet known. We only knew that if it wasn’t working women had a high risk of breast and ovarian cancer. That’s why the gene was called the BRCA1 gene for BReast CAncer 1 gene.
Setting an example
Genetics is becoming an integral part of medicine and the conversations about genetics are broadening. Of course, it’s unrealistic to expect everyone to know everything about genetics, and it’s inevitable that people will continue to say “the gene for…” .
But we can set an example by using the correct language wherever possible, particularly in official materials from research and patient representative organisations. We need to do this because we increasingly need to have deeper, more detailed conversations about the impact of DNA sequence changes in genes. Having to first explain that the assumption of ‘having the gene for’ their disease is not correct adds complexity and confusion, and can reduce confidence. We should try to avoid this.