Trisomy facts for kids
A trisomy is when there are three copies of a chromosome. Normally in humans there is only two copies of any given chromosome. The most notable condition is Trisomy 21 syndrome which is better known as Down Syndrome, a form of developmental genetic disorder.
Images for kids
Karyotype of a human with Trisomy 21 (Down syndrome)
Trisomy Facts for Kids. Kiddle Encyclopedia.