Question

A person with Down Syndrome has an additional #21 chromosome in every somatic cell. This condition is also called trisomy 21. The cause of this syndrome

Answer 1

is an error in cell division called non-disjunction. 

Answer 2

The answer is C.) Is through the union of a normal gamete with a haploid amount of chromosomes (n) and another gamete with an extra #21 (n+1)