Which of the following statements is true of Down's syndrome?
A) Down's syndrome is usually caused by a defect in the sex chromosomes of an individual.
B) The symptoms of Down's syndrome are similar to those of Sickle cell.
C) Down's syndrome is caused by a sexually transmitted infection (STI) during conception.
D) The probability of having a child with Down's syndrome increases with the age of the parents.

Question

Quizplus · Accepted Answer

Down's syndrome is primarily caused by an extra copy of chromosome 21 (trisomy 21), not by defects in sex chromosomes or sexually transmitted infections. The risk of having a child with Down's syndrome does indeed increase with the age of the parents, especially the mother.

Which of the Following Statements Is True of Down's Syndrome