Written by the Fiveable Content Team • Last updated September 2025
Verified for the 2026 exam
Verified for the 2026 exam•Written by the Fiveable Content Team • Last updated September 2025
Definition
Trisomy 21, also known as Down syndrome, is a genetic disorder caused by the presence an extra 21st chromosome.
Related terms
Karyotype: The number and visual appearance of the chromosomes in the cell nuclei of an organism or species.
Non-disjunction: The failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei.
Genetic Disorder: A disease caused by abnormalities in an individual’s genetic material (genome).