Aneuploidy is a genetic condition where an individual has an abnormal number of chromosomes. Normally, humans have 46 chromosomes, arranged in 23 pairs. In aneuploidy, there may be an extra chromosome (trisomy) or a missing chromosome (monosomy), leading to various health issues. Common examples of aneuploidy include Down syndrome, which is caused by an extra copy of chromosome 21, and Turner syndrome, resulting from a missing X chromosome in females. These conditions can affect physical development, cognitive abilities, and overall health, highlighting the importance of proper chromosome number for normal biological function.