Down syndrome, a genetic condition affecting development, is often misunderstood. While we see its effects, what *causes* it? The answer lies in our chromosomes. Typically, humans have 46 chromosomes arranged in 23 pairs. Down syndrome most often occurs when a person has an extra copy of chromosome 21 (Trisomy 21). This extra chromosome disrupts the normal course of development.
But *why* does this happen? In most cases (around 95%), Trisomy 21 is caused by a random error in cell division during the formation of the egg or sperm. This error, called nondisjunction, means one of the gametes (egg or sperm) ends up with an extra chromosome 21. After fertilization, the resulting embryo has three copies of chromosome 21 instead of the usual two.
It's important to understand that Down syndrome is *not* caused by anything the parents did or didn't do before or during pregnancy. It's a random genetic event. While the risk of having a child with Down syndrome slightly increases with the mother's age, it can happen to anyone. Understanding the cause helps remove stigma and promotes a more informed and compassionate perspective.
