Trisomies
Our bodies are made up of trillions of cells. Within each cell is our genetic material, known as DNA. DNA contains the instructions that guide our bodies in how to grow and develop. It is organized into structures called chromosomes. We inherit our chromosomes from our parents. Healthy humans typically have 46 chromosomes, arranged in 23 pairs. Females have two X chromosomes, while males have one X and one Y chromosome. Sometimes, an error occurs during the formation of an egg or sperm cell, resulting in an extra or missing chromosome. If this happens, the pregnancy may also have an abnormal number of chromosomes. A trisomy can occur in any chromosome from 1 to 22, as well as in the sex chromosomes.
