Nondisjunction is a genetic error that occurs when chromosomes fail to separate properly during cell division. This can happen during either meiosis or mitosis, leading to cells with an abnormal number of chromosomes. If nondisjunction occurs in gametes, it can result in offspring with conditions such as Down syndrome, which is caused by an extra copy of chromosome 21. When nondisjunction happens, it can lead to various genetic disorders depending on which chromosomes are affected. The resulting cells may have too many or too few chromosomes, causing developmental issues and health problems. Understanding nondisjunction is important for studying genetic diseases and their inheritance patterns.