Alzheimer's disease is a debilitating mental illness caused by a single misplaced nucleotide among the billions of nucleotides that make up a human's genetic code. Modern science has developed methods to test for Alzheimer's disease as young as thirty, which obviously cannot cure the person in question, but early diagnosis warns a potential parent that he or she possesses a genetic mutation that she has a 50/50 chance of passing onto her child. Doctors are also able to use a similar genetic test to screen fertilized embryos cultured in vitro to see if they possess the defective gene. To make efficient use of this testing mechanism, numerous eggs are removed from the ovaries of the woman in question and are fertilized in vitro. The fertilized eggs are allowed to grow into into the 8-cell or 16-cell blastomere stage and are then tested for possession of the defective genes. Once a healthy embryo is found, it is implanted in the uterus of its parent and develops into a baby who has no risk of developing Alzheimer's disease. (11)