It's easy to fall into the trap of talking about "the gene for" a disease, but the truth is that a lot of diseases are influenced both by genetics and by other factors in your life. This infographic from Mosaic explains what that means.
Take breast cancer, for example. We all have a gene for the BRCA1 protein, and in most of us that protein acts as a powerful tumour suppressor: it's a good guy protecting us from cancer. But if you get a certain "variant" of BRCA1, or its cousin BRCA2, that tumour suppressor won't be able to do its job as well, and you'll be at higher risk of breast cancer.
Mosaic's infographic puts some numbers on that risk. Only 1 in 500 people have versions of BRCA1 or BRCA2 that put them at higher risk. What that means: Among people with a defective version, their risk of cancer averages 1 in 2 — so a coin flip, not a death sentence. Among people with totally normal BRCA1 and BRCA2 proteins, breast cancer risk isn't gone; it's still 1 in 8. Genes influence risk, but they don't totally determine your fate.
Sure, some (like Huntington's) are close to guarantees, but most reflect a give-and-take between genes and everything else in your life. For example, obesity raises your heart disease risk by 69 per cent, while the MTHFR gene variant can only bump it up by 16 per cent.
Here's the full infographic. Check out the link below for Mosaic's explanation and the sources for their numbers.
Genetics: Risk or Destiny? [Mosaic]