A chromosomal condition where the total number of chromosomes is not a multiple of the haploid number, resulting from the gain or loss of individual chromosomes. This condition often leads to developmental abnormalities or genetic disorders.
From Greek 'an-' meaning 'not' or 'without' and 'eu' meaning 'good' or 'true,' combined with 'ploidy' referring to chromosome sets. The term was developed in the 20th century to describe abnormal chromosome numbers that deviate from normal diploid or polyploid states.
Down syndrome is caused by trisomy 21 - having three copies of chromosome 21 instead of two - showing how even a single extra chromosome can have profound effects! It demonstrates how precisely balanced our chromosome numbers need to be for normal development.
Complete word intelligence in one call. Free tier — 50 lookups/day.