About Genes, DNA, and Cancer
Our bodies are made up of cells, and genes are part of our cells. Each person has 20,000-25,000 genes. We have genes that determine certain aspects of our appearance, such as eye color and hair color, and we have other genes that play a role in our general health and cancer risk.
Genes are made of DNA that tells our cells what to do. DNA, also called genetic material, is made up of four chemical bases represented by the letters A, T, C, and G. These bases form the genetic alphabet that combines in different patterns to "spell out" our genes. As the cells in our bodies grow and divide, each makes a copy of its DNA to pass on to the new cells.
If genetic material becomes damaged, it can change how a cell functions. Genetic changes (called mutations) can lead to cancer if they occur in specific areas of DNA that control cell growth, death, and repair.
Hereditary Cancer Risk
Hereditary cancer risk comes from genetic changes that people inherit from their mother or father. A hereditary risk factor may be passed down through family generations, though only 5-10% of all cancers are caused by known inherited genetic changes.
Common Questions about Genetics and Cancer
How are genetic changes passed down in families?
Genes come in pairs. In the cells involved in reproduction (egg cells in females and sperm cells in males), these pairs are separated. Each egg or sperm cell contains only one-half of the parent's genes. When egg and sperm meet, the embryo has the full number of genes—half of them from the mother and half from the father. If there is a genetic change (a mutation) in either of the parents' DNA, this may also be passed down to the child.
How can a genetic change cause cancer?
Cancers are caused by genetic mutations that occur in a cell. A variety of things may cause mutations: normal aging, substances in our environment, or copying mistakes when cells divide. If these mutations happen in genes that play an important role in regulating functions such as cell growth, cancer may occur. Usually mutations are required in several different genes before a cell becomes cancerous. Most cancers arise from mutations in a single cell that accumulate due to chance or other factors. Mutations like these that occur only in one cell cannot be passed on to one's children, and thus they are not considered hereditary. However, some people are born with a mutation in a particular gene in every cell of the body, and this makes the person much more likely to develop one or more cancers over their lifetime. This is also the reason why some families have patterns of different types of cancer in the family; having a mutation in every cell can predispose a person or family to several different types of cancer. These mutations can be passed on to one's children because they are in every cell, including the sperm or egg cells.
How do I know if my family has an increased risk for cancer?
Families that have increased risks for cancer often have certain similarities:
- Cancer occurring at an earlier age than in the general population (for example, breast or colon cancer before age 50)
- Multiple close family members with either the same type of cancer or related cancers (for example, breast and ovarian cancer; colon and uterine cancer)
- More than one type of cancer in the same person (for example, melanoma and pancreatic cancer)
- A close family member with multiple primary cancers of one type, such as bilateral breast cancer (breast cancer occurring in both breasts) or a single family member with two separate melanomas
- Rare cancers in the family
- Multiple generations with cancer
- One or more family members with multiple precancerous findings (for example, 10 or more colon polyps over a lifetime)
Individuals or families with these features may consider having a genetic evaluation to learn more about their cancer risk. To learn about a genetic evaluation, contact our Family Cancer Assessment Clinic (FCAC). The FCAC identifies and helps families who have an increased risk for cancer.
What is an FCAC appointment like?
Before the appointment, patients will be asked to complete a questionnaire with information about their personal health history and a detailed questionnaire about their family history. FCAC may request certain medical records, which require patients to sign a release form.
During the appointment, patients will meet with a Huntsman Cancer Institute (HCI) genetic counselor. The genetic counselor will review the patient's personal and family history to determine whether the family could have a hereditary risk for cancer. They will discuss available genetic testing options, including the risks and benefits of genetic testing.
If patients decide to pursue genetic testing, the genetic counselor can guide them through the process. Counselors will discuss how hereditary cancer risks can be managed through screening and preventive options. Usually, an HCI physician will be available to answer additional questions. Our genetic counselors can also provide patients with helpful educational and support resources as well as information about the opportunity to participate in research.
What is genetic testing?
Genes are the parts of cells that hold the instructions for the body to function properly. Genetic testing looks for changes in genes (called mutations) that increase the risk of developing cancer. These mutations can be passed down through families, making some family members more likely to develop cancer than people in the general population.
What does genetic testing involve?
The test usually requires a small blood sample. Sometimes other specimens, such as cells from a cheek swab, can be used. The sample is sent to a laboratory for analysis. Results come back to the FCAC and will be shared with the patient, along with any additional management and follow-up recommendations.
Is genetic testing recommended for everyone?
Genetic testing is available to everyone, but it is not always recommended. A genetic counselor and physician are available to talk with a patient about the benefits and limitations of genetic testing based on personal and family history. Ultimately each person has the final decision about whether to proceed with testing.
Will my health insurance cover genetic testing?
Every health insurance policy is different. Scheduling an appointment a few weeks in advance allows the FCAC staff time to contact the insurance company to pre-authorize a specific genetic test. If the policy does not cover genetic testing, other options such as self-payment or testing other family members who are insured may be available. The FCAC can also provide screening recommendations for a patient and their family based on family history alone.
When genetic testing has confirmed a hereditary cancer predisposition, most insurance companies will pay for recommended screenings and treatments.
Will I have problems keeping or obtaining health insurance if I have genetic testing?
The Federal Health Insurance Privacy and Accountability Act (HIPAA) protects the privacy of genetic information. In addition, Utah has a strong state law, the Genetic Privacy Act, which makes it illegal for health insurance companies or employers to use a person’s genetic test results against them. This means employers cannot fire a person and a health insurance company cannot cancel a person’s policy or raise premiums because of a positive genetic test result. This protection extends to both group and private insurance policies. Find a copy of Utah’s law at http://le.utah.gov/~code/TITLE26/26_45.htm. Beyond this state law, there is a federal law titled the Genetic Information Nondiscrimination Act (GINA) that was signed into law in 2008. This law also protects against health insurance and employment discrimination. You can find more information about this law at http://www.genome.gov/24519851.
Where to Turn with Your Questions or Concerns
The information was written by staff in the Family Cancer Assessment Clinic.