Down syndrome most commonly results from
A)a failure of the twenty-first pair of chromosomes to separate during meiosis.
B)increased age of the father.
C)oxygen deprivation during or immediately after birth.
D)mutation of the genetic material on the twenty-third chromosomal pair.

Question

Quizplus · Accepted Answer

Down syndrome is caused by the presence of an extra copy of chromosome 21, which is also known as trisomy 21. This occurs when the twenty-first pair of chromosomes fails to separate during meiosis, leading to the presence of three copies of chromosome 21 instead of the usual two. This is the most common cause of Down syndrome, accounting for around 95% of cases. Increased age of the mother is a known risk factor for Down syndrome, but it is not the cause. Oxygen deprivation during birth or mutation of genetic material on the twenty-third chromosomal pair are not associated with Down syndrome.

Down Syndrome Most Commonly Results from