Section 5- Solution key: 1. In the box below, write the most likely mode of inheritance of the following pedigree? 1 2 3 4 Autosomal recessive 5 6 7 8 ? Given each consistent mode of inheritance, if the couple in question decides to have a child, what is the probability of that child being affected? (Note: Use the uppercase or lowercase A to represent the alleles for the dominant and recessive traits). The probability of individual 6 being a carrier is 2/3 and person 7 is a carrier. If they are both carriers then the probability of their child being a carrier is ¼. So the overall probability of their child being a carrier is ( 2/3 X 1X ¼) =1/6. 2. Consider the pedigree below showing the inheritance of two X-linked diseases, hemophilia A and hemophilia B. Hemophilia A is due to a lack of one clotting factor, and hemophilia B is due to a lack of a different clotting factor. Each clotting factor is a protein that is encoded by a specific gene located on the X chromosome. Note that no individual shown in this pedigree is affected with both hemophilia A and hemophila B. 2 1 Phenotypically normal 3 4 Affected with Hemophilia A Affected with hemophilia B 5 a) Write the genotypes for the following individuals at both the hemophilia A and hemophilia B disease loci. Clearly define your genotype symbols. Individual 1 2 3 4 5 Genotype XaBY XAbXAB XAbY XaBXAb XABY b) How do you account for individual 5 not being affected with either hemophilia A or hemophilia B? Individual #5 is the product of a fusion of a sperm with an egg from individual 4that had undergone recombination between the A and the B genes during meiosis 1.