WHAT CAUSES ABNORMAL NUMBERS OF CHROMOSOMES?
Chromosomes are tiny structures in the cells of the human body that contain roughly 30,000 to 35,000 gene pairs. The genes determine traits like eye and hair color, and also how our bodies grow and develop in the womb. Each person normally has 23 pairs of chromosomes (46 in all), inheriting one chromosome per pair from each parent. Unlike other cells in the body, sperm and egg cells only have 23 unpaired chromosomes; when a sperm and egg unite, they form a fertilized egg with all 46 chromosomes. Sometimes, in the process of cell division, an error occurs, so a sperm or egg cell has too many or too few chromosomes. Scientists don’t know what exactly causes this, but the resulting embryo has a chromosomal abnormality. About 70 percent of such pregnancies result in a miscarriage, but if carried to term, the baby could have any number of disorders because of the abnormality. ABOUT DOWN SYNDROME AND CHROMOSOMAL ABNORMALITIES: Down syndrome is the most common of these disorders, affecting ab
