Most humans have 23 pairs of chromosomes within each cell; all of which are inherited from our parents. One of the chromosomes from every pair has been inherited from the mother, and the other from the father. Our chromosomes form our genes and they determine everything from our gender (XX chromosomes for female, XY for male), eye colour and hair colour through to our behavioural characteristics. They hold complex instructions for the growth and development of every cell in our bodies. While this phenomenon displays wildly interesting details about how our bodies grow and work, perhaps more fascinating is how the study of our genes can uncover an abundance of information about our health.
Hereditary genetic disorders, mutations and diseases
Along with physical traits from our parents, genetic disorders can also be inherited. These are caused by a change in DNA. Some hereditary diseases can be present at birth while others may develop later in an individual’s life. In some cases, a person can only inherit a genetic disorder if both parents have a copy of the faulty gene in question. This is referred to as autosomal recessive inheritance and includes conditions such as cystic fibrosis, sickle cell anaemia and Tay-Sachs disease (a potentially fatal condition that causes progressive damage to the nervous system). In this scenario, there is a one in four chance that a person will inherit the genetic condition and a 50 percent chance that they will be a carrier. Autosomal dominant inheritance, on the other hand, determines that just one parent needs to be a carrier of a mutation or genetic disorder in order for the condition to be inherited by their children. This particular pattern carries higher risks in that there is a 50 percent chance that the mutation will be passed on. Diseases inherited in this way include tuberous sclerosis (a condition that causes usually benign tumours to develop in the body) and Huntington’s disease (a disease that damages nerve cells in the brain, affecting movement, cognition and behaviour). In some cases, individuals may have inherited faulty genes that increase their risk of developing cancer. Genetic testing is available for a wide range of cancers—including breast and ovarian cancer—and can help determine an individual’s chance of developing it.
Genes and mental health
Our mental wellbeing significantly impacts the way in which we think and feel. The National Institute of Mental Health (NIMH) found that poor mental health is a direct result of environmental, biological, psychological and genetic factors. In 2013, a study conducted by the Cross-Disorder Group of the Psychiatric Genomics Consortium found that along with autism, ADHD, bipolar disorder and schizophrenia, clinical depression is closely linked to our genetics. This conclusion came after researchers found variations on four genetic regions when studying the DNA of those with these common mental disorders. While having family members with one of these conditions does not necessarily dictate that you will ever suffer from these disorders yourself, the predisposition may increase your risk of developing them. Learn about your family’s mental health history so that you can understand and spot early signs of potential issues to better manage them.
Genetic testing—or DNA testing—involves testing samples of blood, hair, skin, saliva, amniotic fluid or other tissues for particular changes in the DNA that can signify genetic disorders. There are various reasons an individual may want to undertake genetic testing, including:
Prenatal testing. This allows doctors to uncover potential genetic diseases in foetuses.
Carrier testing. Prospective parents can test to see whether they carry a genetic mutation that could be passed on to future children.
Predictive genetic testing. Patients can test for genetic diseases even without showing any symptoms. This is most commonly carried out if a specific disease runs in the family.
Gene therapy is a technique that allows doctors or surgeons to treat diseases by inserting genes into a patient’s cells in place of using medication. Depending on the disease or disorder, the procedure—which is currently in its experimental stages—may replace a faulty gene, inactivate a mutated gene that doesn’t function properly or introduce a new gene into a cell. The concept of gene therapy is relatively new in the medical arena and still requires further study as it carries high risks. According to Genetics Home Reference, ‘gene therapy is currently being tested only for diseases that have no other cures’.