Genetic Family History 101
09 Aug 2004
How much should you worry if your father died of a heart attack at age 50? Or your mother developed breast cancer at 40 years of age? Or a brother required surgery for malignancy of the colon at an early age? Or there’s a strong family history of diabetes or osteoporosis? In these cases how beneficial is genetic testing?
Today, with an aging population, it would be most unusual for a family to say none have died from cancer, heart attack, stroke, diabetes or suffered from mental illness. So there’s no need for sleepless nights unless there’s an unusual strong family history of one of these diseases. And if the death of a relative occurred at 40 years of age, it matters more than if death happened at 80.
Our inherited genes provide the basic blueprint of our life. Human cells contain 46 chromosomes arranged in 23 pairs. Each pair has one chromosome from the father and one from the mother. Each chromosome contains thousands of genes composed of DNA, “the molecules of life”. Researchers have now mapped out the entire human genome.
Genetic testing is an immense benefit in certain situations. A pregnant woman can be told her child is going to be born with Down’s Syndrome. Or a parent with a dominant gene for Huntington’s Chorea, a severe nervous affliction, can be told there’s a 50 per cent chance a child will inherit this condition.
What about common problems such as breast cancer? It’s estimated that about 5 per of breast cancers can be traced to a breast cancer gene. But if a 30 year old woman is told the gene is present she faces a dicey question.
Her breasts can be surgically removed. But this drastic approach does not always prevent malignancy. Moreover, genes never tell you when the cancer will develop and it may not happen until 80 years of age. Some women decide it’s better not to know the gene is present.
Researchers believe they may also have discovered a gene for Alzheimer’s disease. But if that’s the case, there’s no way at the moment to surgically remove this problem. So do you really want to know if it’s present?
In other cases it would madness to bury your head in the sand. Some families have a strong history of large bowel cancer. By being aware that the faulty gene is present regular colonoscopies can save lives by detecting and removing polyps long before they become malignant.
Things get more complicated when dealing with chronic disorders such as heart attack, diabetes, and osteoporosis. In these diseases more than one gene may be involved and it’s still unknown how much depends on genetics and how much on environment and lifestyle.
For years I’ve been concerned about the increasing amount of radiation received by patients. Some helps to detect early cancers and saves lives. But today many x-rays are ordered simply because of medical legal or trivial reasons. In addition, there are increasing numbers of diagnostic techniques that are dependent on radiation. The unsolved question is whether greater use of radiation will cause genetic damage and later malignancies. So it’s prudent not to ask the doctor, “Can’t you order an X-ray.”
Today, people are becoming ill more from faulty lifestyle than faulty genes. For instance, the gene for type 2 diabetes may not produce this disease if you don’t gain weight. And if a gene is discovered for osteoporosis, it’s possible it could be inhibited by drinking three glasses of milk a day, adequate amounts of vitamin D and regular exercise.
At the moment a look at family history behaviour provides better clues about what the future holds than genetics. Check to see if those who died prematurely from heart disease were also chain-smokers and couch potatoes for years. And were relatives who developed diabetes also those who became obese in mid-life.
You may discover that Pogo was right when he shrewdly remarked that “We have discovered the enemy and the enemy is us.” All too often today we are the architects of our own destruction, not our genes.
