MOST diagnosed cases of Down syndrome are of the:

A) trisomy 21 type.
B) mosaicism type.
C) age-related type.
D) translocation type.

Trisomy 21

A genetic disorder caused by the presence of an extra 21st chromosome, also known as Down syndrome, leading to developmental and physical changes.

Mosaicism

A condition in which cells within the same person have a different genetic makeup, caused by mutations occurring after fertilization.

Translocation

In genetics, the process or result of a chromosome segment moving to a different position within the same or another chromosome.