Practice: Work on for next class. Tay-Sachs disease (Infantile amaurotic Idiocy) is a rare human disease in which toxic substances accumulate in nerve cells. The recessive allele responsible for the disease is inherited in a simple Mendelian manner. For unknown reasons, the allele is more common in populations of Ashkenazi Jews of eastern Europe. A woman is planning to marry her first cousin, but the couple discovers that their shared grandfather’s sister died in infancy of Tay-Sachs disease. Do not refer to the solutions manual for this question – it is incorrect. Draw the relevant parts of the pedigree, and show all the genotypes as completely as possible. What is the probability that the shared grandfather is a carrier of the Tay-Sachs allele? What is the probability that the cousins’ first child will have Tay-Sachs disease, assuming that all people who marry into the family are homozygous dominant?