Review Questions on "Nondisjunction":

  1. What is nondisjunction?
  2. At what two stages during meiosis can it occur?
  3. Under what circumstances can a human embryo survive if it is missing a chromosome (i.e., if it only has 45, instead of the normal 46, chromosomes)?
  4. What usually happens if a human embryo inherits an extra chromosome (i.e., if it has 47, instead of the normal 46 chromosomes)?
  5. What causes Down's Syndrome?
  6. What traits are common to males and females that possess an extra X chromosome?
  7. What is a mosaicism?  What causes it?
  8. What usually happens if a child is born with more than one extra sex chromosome (e.g. XXXX, XXXY, XXYY)?
  9. What usually happens if two sperm fertilize one egg?