Slide show: How genetic disorders are inherited

Your body is made up of trillions of cells. Each cell has a core structure (nucleus) that contains your chromosomes.

Each chromosome is made up of tightly coiled strands of deoxyribonucleic acid (DNA). Genes are segments of DNA that determine specific traits, such as eye or hair color. You have more than 20,000 genes. You have two copies of each gene — one inherited from each of your parents.

A variant is a change in your DNA. Some variants are benign — they're not associated with health problems. Other variants are pathogenic — they're associated with a genetic or health condition. Pathogenic variants are sometimes called mutations.

Many types of pathogenic variants cause a change in or damage to a gene. These abnormal genes (gene mutations) can be inherited or acquired. Acquired gene mutations may be associated with environmental exposures. We often don't understand the specific exposures that result in an acquired gene mutation.