We’ve all been to a family reunion and politely smiled as longdistance relatives tell us how much we resemble our parents. But while it’s often obvious early in life that you inherited your mother’s hair colour or your father’s laugh, it’s usually not until later on that the genes we’ve inherited start to make themselves known.
These genes can determine the likelihood of developing certain diseases, including diabetes, heart disease, Alzheimer’s and cancer. This means that, while we can all benefit from maintaining a healthy lifestyle, there are some aspects of our health we’re less able to control.
“The role our genes play as we get older is very complex, and varies between one person to the next,” according to Leigh Jackson, lecturer in genomic medicine at the University of Exeter Medical School.
We pick up gene faults through life as our cells multiply, whether from environmental factors such as UV light, X-rays and smoking, or from our cells making errors as they copy our DNA.
“We have specific proteins that go along the DNA and fix mistakes, and problems can occur when someone gets a fault in the DNA that makes these proteins,” Jackson says. “This prevents the DNA from getting fixed as well as it should, which can lead to various cancers. This fault can be inherited from our parents or acquired throughout life.”
Health conditions can be broadly separated into those caused by faults in a single gene and those caused by the influence of many genes and the environment. Some single-gene disorders are dominant and require only one fault to be inherited from either parent, and others are recessive and require two faults to be inherited, one from each parent.
“Dominant conditions are those where you might see many family members across the generations having the same disease, whereas recessive conditions may only pop up once with no previous family history,” Jackson says.
When it comes to the most common diseases we can inherit from our parents, research shows genetics and lifestyle can both play similar roles.
There are many different genetic factors that contribute to cardiovascular health, Jackson says. A person with a high genetic risk of developing the disease will benefit hugely from a healthy lifestyle, and often this can cancel out any increased genetic risk.
“As with most things in genetics there’s no one answer, but generally a healthy lifestyle will be beneficial regardless of genetic predisposition, and sometimes even more beneficial if at high genetic risk.”
Inside most of our cells is a nucleus with 23 pairs of chromosomes made up of genes that control our cells and bodies. Cancer develops when something goes wrong with one or more genes in a cell. Most gene faults are caused by environmental factors, such as smoking or exposure to sunlight, but some can be inherited from a parent. If a parent has a gene fault, there is a 50 percent chance they’ll pass it onto their offspring. This doesn’t mean their child will definitely get the disease, but they have a higher risk of developing certain types of cancer.
Research has found that the more close family members you have who develop Alzheimer’s disease, the more likely you are to go on to develop it yourself, according to Aoife Kiely, research officer at Alzheimer’s Society. “The genes we know can be faulty and cause Alzheimer’s disease only account for 10 percent of cases, and these would be early-onset cases that develop in a person’s 30s, 40s and 60s, and caused by mutations in three main genes,” Kiely says.
But researchers aren’t yet sure what causes the remaining 90 percent of cases.
“They could be caused by another gene variation, because while we all have same set of genes, some can vary slightly between different people, and sometimes these can cause subtle enough changes to increase risk for disease. “On top of that, there are other lifestyle and environmental risk factors, such as diabetes, depression, cardiovascular disease and smoking, which could snowball together to cause a greater risk of Alzheimer’s, but it’s difficult to define.” What we do know, Kiely tells us, is that research looking into prevention shows connections between brain and heart health.
“What’s good for the heart, is good for the head, so we recommend following a heart-healthy diet, such as the Mediterranean diet, which is low in unhealthy fats, alcohol and sugar and has lots of healthy lean meats, vegetables and fish, as well as stopping smoking, and not drinking alcohol to excess.”