Which of the Following is FALSE of Down Syndrome

Question

Which of the following is FALSE of Down syndrome?
A) There are homologs in model organisms, such as mice and Drosophila, for genes in the Down syndrome critical region (DSCR).
B) Studying individuals with partial trisomy of chromosome 21 identified the Down syndrome critical region (DSCR) with a small number of genes responsible for the principal symptoms.
C) Down syndrome is the most common triploidy (3n) in which individuals have three sets of chromosomes.
D) Molecular genetic analysis of the chromosomes in infants with trisomy 21 determined that the majority of cases were attributable to maternal nondisjunction in meiosis I.
E) There is a link between the increased risk of Down syndrome and increased maternal age at conception.

Accepted Answer

Down syndrome is characterized by trisomy 21, where individuals have three copies of chromosome 21, not triploidy (3n), where individuals would have three complete sets of chromosomes.