Down's syndrome is caused by what genetic condition?

Down's syndrome is caused by the presence of an extra copy of chromosome 21, which is known as trisomy 21. This means that instead of the typical two copies of chromosome 21, individuals with Down's syndrome have three copies. This genetic anomaly occurs due to nondisjunction, which is the failure of chromosome pairs to separate properly during cell division, leading to the fertilized egg having an abnormal number of chromosomes. This extra genetic material affects physical and cognitive development, resulting in the characteristics associated with Down's syndrome. Understanding this genetic basis is crucial for recognizing the implications it has on health and development in affected individuals.