The extra 21st chromosome that causes Down syndrome is
A) usually provided by the egg.
B) usually provided by the sperm.
C) provided by the egg about half the time and by the sperm about half the time.
D) usually created sometime during prenatal development.

Question

Quizplus · Accepted Answer

The extra 21st chromosome causing Down syndrome is usually provided by the egg. This is due to nondisjunction during meiosis in the mother, which is more likely to occur as maternal age increases.

The Extra 21st Chromosome That Causes Down Syndrome Is