The Human Genome Project estimates that we have about 20,000 genes. The genes in our DNA are like a toolkit, used by different cells in different ways. Most cells use only a few of the many, many possible functions of our genes.
We’re all familiar with the phrase “it runs in the family.” From an obvious family resemblance to a not-so-obvious inherited trait such as the shape of our earlobes, much of who we are physically coming from our DNA, which comes from the DNA of our biological parents.
The Human Genome Project estimates that we have about 20,000 genes. The genes in our DNA are like a toolkit, used by different cells in different ways. Most cells use only a few of the many, many possible functions of our genes.
All of Your Cells Contain Your DNA*
*Except red blood cells.
Genes Can Change
All cancers are caused by harmful mutations or changes in DNA. Mutations in DNA happen regularly, but most of these changes are not harmful and do not cause cancer. The changes usually occur by chance; for example, when cells divide to produce new cells, a mistake in cell division could introduce a tiny change. Fortunately, these mutations are usually automatically repaired by your body.
Sometimes, however, the mutation is not repaired and is passed on when the cell divides. If the mutation is harmful and interferes with a critical function, such as regulating cell growth or DNA repair, the mutation can make the cells more cancer-like. If enough of these mutations occur in a cell, cancer may be the result.
“All cancer is genetic, in that it is triggered by altered genes. Genes that control the orderly replication of cells become damaged, allowing the cells to reproduce without restraint.”
— National Cancer Institute, National Institutes of Health
Mutations Sometimes Lead to Cancer
As shown above, a series of random mutations can create cancer cells. Mutations can also be part of your genetic makeup from birth.
Two kinds of gene mutations are important in cancer:
Random—the mistakes that occur in DNA by chance and are repeated as the cell divides. These mistakes are more likely to accumulate as you get older. Being exposed to radiation or certain chemicals can also make genetic changes more likely.
Inherited—the genetic mutations a person is born with that are passed on by the person’s father or mother, or both
Most cancers develop from random mutations, but up to 10 percent are inherited, or hereditary. Certain inherited genetic mutations can make it much more likely that someone with the mutation will get cancer, as well as develop it earlier or even develop multiple cancers in their lifetime.
Sometimes, however, a family will appear to have hereditary cancer when what they actually share is a living or working environment that exposes them to radiation or chemicals that can cause mutations. Your healthcare professional can help you determine which could be true in your case.
If you do carry an inherited mutation that has been linked to cancer, knowing your risk of cancer can help you and your healthcare professional make better, more informed decisions about your healthcare, possibly before cancer has even a had chance to develop.
Family History
When talking about your genetic family history, the only family members who matter are your biological relatives. For example, your father is a biological first-degree relative to his biological brother, your uncle is a biological second-degree relative. If he marries a woman, she becomes your aunt, but she is not a biological relative. If they have a child, however, that child is your first cousin and a biological third-degree relative.
Which Relatives Are Important When Thinking About Hereditary Risk?
People with a family health history of a particular disease can take action to reduce their risk of developing that disease. To learn more about your biological inheritance, talk to your relatives, gather information on their health history and fill out a family tree. If you find that certain illnesses, such as breast or ovarian cancer, have appeared in more than one relative, you should talk with your healthcare professional and investigate the possibility of hereditary cancer.
Biological mother, biological father, full biological sibling, or biological child (stepparents, stepchildren, or half-siblings are not first-degree relatives)
Biological grandparents, biological aunts, and uncles, biological nieces and nephews, half-siblings, or biological grandchildren
Biological first cousins, great-grandparents, great-aunts and great-uncles
Research has shown that up to 10 percent of cancers are due to factors that are passed from one generation to the next. These syndromes are known as hereditary cancers and there are genetic tests that can be used to determine an individual’s risk for developing these cancers. If you suspect that you or someone you know may be at risk for cancer –- such as a family history of cancer or membership in an at-risk ethnic population (such as people with Ashkenazi Jewish ancestry) –- you may want to talk to your healthcare professional about genetic testing.
There are many benefits to getting tested, regardless of the eventual result. If one of your family members — however distant — had cancer, there is a chance that you inherited a gene mutation that not only increases your personal risk of cancer, but also could be passed to the next generation. Those who are carriers of hereditary cancer gene mutations could be at risk of getting cancer earlier in life than the general population. The sooner genetic testing is done, the more likely it is that the risk can be managed appropriately.
Remember: Your healthcare professional is your most valuable source of information and advice about hereditary cancer screening.
