What is DNA, genes and hereditary cancer?

We all have a ‘blueprint’ with instructions for our body to function properly. This ‘blueprint’ is what makes us all different and unique. Our ‘blueprint’ consists of 23 pairs of chromosomes (46 total) within the cells in our body. We get one set of 23 chromosomes from each of our parents and we pass on one chromosome from each pair (half of our chromosomes) to each of our children. Small differences in the genes that make up our DNA are what make us unique. Most differences are called genetic variants and are normal and common. These variants can produce the diverse traits we see in the population (e.g., eye color, height, skin color, etc.). However, sometimes these gene variants (also called mutations) can cause health problems. Most people are born with two normal copies of each gene. Hereditary cancers occur when a person is born with changes or mutations in one copy of a damage-controlling gene which normally protects against cancer. In the majority of these cases, the changes were inherited from the mother or father.

People with gene mutations have a 50% chance of passing the mutation to each of their children.

These changes can increase the risk for cancers in different parts of the body, but they do not increase the risk for every type of cancer, and not everyone who is born with a mutation will develop cancer. Cancer is a common disease, so most families will have some members who have had cancer but that does not mean the cancer in that family is hereditary. The cause of most types of cancer is unknown, but experts believe that about 10% of most cancer types are due to inherited gene changes. Cancer that does not appear to be caused by inherited genes is called “sporadic cancer.” It is believed that most– perhaps 90% of all cancers are sporadic. This means even if cancer does not run in a family, a family member can still be at risk for some type of cancer in his or her lifetime.

According to the American Cancer Society Facts & Figures for 2016, nearly 14.5 million Americans are cancer survivors still living in the US. 1,685,210 new cancer cases are expected to be diagnosed and 595,690 Americans are expected to die of cancer in 2016. This translates to about 1,630 people per day making it the second most common cause of death in the US, exceeded only by heart disease and accounts for nearly 1 of every 4 deaths.