Trisomies
Our bodies are made up of trillions of cells. Inside each cell is our genetic material, or DNA. DNA is the instruction manual that tells our bodies how to grow and develop. Our chromosomes are made of DNA. We inherit our chromosomes from our parents. Healthy humans have 46 chromosomes, or 23 pairs of chromosomes. Women have two X chromosomes, while men have one X chromosome and one Y chromosome. Sometimes a mistake occurs that causes the sperm or egg to have an extra chromosome or a missing chromosome. If this happens, the pregnancy may also have an extra chromosome or a missing chromosome. Trisomies can occur on any of the chromosomes.
