How non disjunction can lead to aneuploidy?

Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division, resulting in an unequal distribution of chromosomes in the daughter cells. When this occurs during meiOSis, it can lead to gametes with an abnormal number of chromosomes. If such a gamete participates in fertilization, the resulting zygote may have an abnormal number of chromosomes, a condition known as aneuploidy. This can lead to various genetic disorders, such as Down syndrome, which is caused by the presence of an extra copy of chromosome 21.