Genes and heredity
The human body is made up of trillions of cells that provide structure for the body, process the nutrients we receive from food, create energy, and perform many other functions. All the cells in the body contain the same genetic material, DNA.
Genes are made up of DNA, and strands of DNA make up the chromosomes that are found in the nucleus of cells. Each person has 46 chromosomes—23 from the mother, and 23 from the father. The Human Genome Project estimates that humans have about 25,000 genes, and has mapped the location of each gene on each chromosome, enabling researchers to identify genes that are associated with different functions.
The genes we inherit from our parents help to determine who we are physically—from the color of our eyes and hair to our susceptibility to certain diseases, including cancer.
How cancer cells get their start
Normal cells divide and duplicate themselves in a very controlled way, but sometimes an error occurs, and the DNA is not copied correctly. Most of the time this error is corrected, or the cell cannot function and is destroyed. Yet sometimes the tiny change in the DNA is not repaired, and the error is passed on when the cell divides to make new cells.
If the change is a mutation that interferes with a critical function such as DNA repair or the regulation of cell growth, then the mutation can make the cells more cancer-like. If enough mutations occur within a cell over time, it can lead to cancer.
Gene mutations and cancer
A gene mutation is a permanent change in the DNA that makes up a particular gene. For cancer, two kinds of gene mutations are important.
- Random (acquired): the mistakes that occur in DNA by chance and get repeated. These mistakes are more likely to happen as people get older. Being exposed to ultraviolet radiation from the sun, or to certain chemicals or environmental elements, can also make random genetic changes more likely.
- Inherited: the genetic changes that a person is born with, usually passed on by the person’s father or mother or both.
Most cancers develop from random mutations, but up to 10% come from inherited genetic changes passed on by a parent. Certain inherited mutations can make it much more likely that a person carrying the mutation will get cancer—and will get cancer earlier.
If you do carry an inherited mutation that has been linked to cancer, knowing your risk can help you and your doctor make better, more informed decisions about your health, possibly before cancer has a chance to develop. It can also help you protect your children and other family members.