Your body is made up of trillions of cells. Within each cell is your genetic material, or DNA. DNA is the instruction manual that tells your body how to grow and develop.
DNA is packaged into structures called chromosomes. You inherit your chromosomes from your parents.
Humans typically have 46 chromosomes, occurring in 23 pairs. Females typically have two X chromosomes and males have one X and one Y chromosome.
Sometimes, an error can occur that leaves a sperm or egg cell with a missing or extra chromosome.
If that happens, the resulting pregnancy may also have a missing or extra chromosome. Generally chromosome conditions are not inherited.