What genetic condition is characterized by the presence of an extra chromosome 21?

Down syndrome, also referred to as trisomy 21, is characterized by the presence of an extra copy of chromosome 21. This genetic condition arises due to an error in cell division known as nondisjunction, where the chromosome pairs fail to separate properly during the formation of egg or sperm cells. As a result, individuals with Down syndrome typically possess three copies of chromosome 21 instead of the usual two.

The additional genetic material impacts development and leads to the characteristic physical traits, cognitive delays, and potential health complications associated with the condition. Each individual with Down syndrome can have a wide spectrum of abilities and health profiles, but they all share the underlying genetic condition caused by the presence of that extra chromosome 21.

The other options provided in the question refer to different concepts or conditions not specifically linked to the extra chromosome 21 characteristic of Down syndrome. Translocation refers to a specific type of chromosomal abnormality, cancer involves a range of diseases characterized by uncontrolled cell growth, and genetic disorder is a broader term that encompasses various inherited conditions, but it does not specifically denote the presence of an extra chromosome 21.