Down syndrome is most commonly caused by
A) advanced maternal or paternal age.
B) an error that occurs in the early stages of mitosis, called mosaic pattern.
C) mutation of the genetic material on the twenty-third chromosome pair.
D) failure of the twenty-first pair of chromosomes to separate during meiosis.

Question

Quizplus · Accepted Answer

Down syndrome is primarily caused by trisomy 21, which occurs when there is a failure of the twenty-first pair of chromosomes to separate during meiosis, leading to an individual having three copies of chromosome 21 instead of the usual two.

Down Syndrome Is Most Commonly Caused by