Down syndrome is a genetic defect caused by what?

Down syndrome, also known as trisomy 21, is primarily caused by the presence of an extra copy of chromosome 21. This triplication leads to the characteristic physical and developmental features associated with Down syndrome. The condition occurs when there is an error in cell division called nondisjunction, which results in a gamete with an extra chromosome. When this gamete fuses with a normal gamete during fertilization, the resulting embryo has three copies of chromosome 21 instead of the typical two.

This triplication affects the development of the brain and body, contributing to the various physical traits and health issues observed in individuals with Down syndrome. Understanding this genetic cause is crucial for recognizing and providing appropriate care to those with the condition, as it informs both medical and supportive interventions tailored to their specific needs.