Which of the following accurately describes Down's syndrome?

Down's syndrome, also known as trisomy 21, is accurately described as a form of aneuploidy characterized by the presence of three copies of chromosome 21. Aneuploidy refers to an abnormal number of chromosomes in a cell, which occurs when there is a failure in the normal separation of chromosomes during cell division, specifically during meiosis. In the case of Down's syndrome, this nondisjunction leads to the individual having an extra copy of chromosome 21, resulting in a total of three copies instead of the typical two.

This genetic condition is associated with a range of physical and intellectual disabilities, as well as various health issues. The presence of this extra genetic material disrupts normal development, leading to the characteristic features and challenges faced by individuals with Down's syndrome.

The other choices do not accurately describe Down's syndrome. Nondisjunction related to sex chromosomes is associated with disorders like Turner syndrome and Klinefelter syndrome, not Down's syndrome. Environmental factors can influence many conditions, but Down's syndrome is primarily a genetic disorder rather than one linked to external factors. Lastly, polyploidy refers to cells that have more than two complete sets of chromosomes, commonly seen in plants, and does not apply to