Trisomy 21 (Down Syndrome)
Definition
Trisomy 21, also known as Down syndrome, is a genetic disorder caused by the presence an extra 21st chromosome.
Analogy
Imagine if you were putting together a puzzle that should have 100 pieces, but there's an extra piece that doesn't fit anywhere. That's what happens in Trisomy 21 - there's an extra chromosome that disrupts the normal pattern.
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).
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