A genetic predisposition is greater genetic likelihood of developing certain things, such as diseases, allergies, temperament, a certain level of intelligence or many other examples. It should be noted that people with genetic predispositions don’t always end up with the things to which they are predisposed. While genes may be a reliable predictor of certain elements, environment or other genes that haven’t been identified are also important. People are predisposed but not assuredly going to express the genes they’ve inherited from parents.
Genetic predisposition should be viewed as distinct from genes that are always expressed. Those who inherit a gene for Huntington’s disease invariably and ultimately will show signs of the illness. A woman who carries a gene that suggests she is more at risk for breast cancer doesn’t have this same surety. She has an increased chance of getting breast cancer than those in the normal population, but she still may never get it. Some genes, like the one for Huntington’s, really aren’t predispositions and are instead going to work if they have been inherited, no matter what.
This distinction is important when analyzing genetic material. It could be vital to know if a person will inherit a serious and/or fatal illness, but a firestorm of debate exists around the issue of judging people by genetic makeup. Genes of family history that suggest higher intelligence, greater risk for heart disease, increased chances of cancer, or elevated risk of mental illness aren’t always sureties. Moreover, people who lack these genetic expressions could still be highly intelligent, more prone to cardiac illness, or likely to get cancer or mental illness.
The nature/nurture argument lies at the heart of debates about genetic predisposition. Environment plays a significant role in the expression of good and bad genes. A person who grows up in an abusive household may not be genetically prone to mental illness, but is certainly environmentally prone to it. The smoker elevates environmental risk for cancer hugely. Even factors like when women have their first children and whether they breastfeed may decrease or elevate risk for breast cancer.
One concern with evaluating genetic predisposition via gene testing is that it will be used to discriminate against others. Health insurance companies could demand genetic testing and prune from their rolls anyone who has genes that might suggest elevated risk for disease. Employers could refuse to hire those who might need more time off if they got specific illnesses, or they could screen for people with greater likelihood of intelligence. Countries like the US have signed laws prohibiting discrimination based on genetic factors, but as with any other form of discrimination, it’s still possible to break or circumvent these laws.
