One of the most common causes of Down Syndrome is trisomy 21 (an extra copy of the 21st chromosome) caused by a chromosomal nondisjunction error (when chromosom

One of the most common causes of Down Syndrome is trisomy 21 (an extra copy of the 21st chromosome) caused by a chromosomal nondisjunction error (when chromosomes fail to separate properly during meiosis). In the most strictly literal sense, aborting fetuses with Down Snydrome is not eugenics, because it's not altering the allele frequency in the gene pool. That said, I can see why people are uncomfortable with it.