ExplanationA. False. If the disorde

ExplanationA. False. If the disorder is autosomal recessive then three people Ⅰ1, Ⅱ7 and Ⅲ5 must be carriers. Heterozygotes should not be so common because it is a rare disorder.Therefore, it is not likely the disorder is caused by a recessive allele. The disorder is actually caused by a dominant allele.B. False. The disorder is caused by recessive alleles. Persons IV5 and IVe wererecessive homozygotes but none of their children was affected. It indicates thatthere is complementation between recessive alleles of different genes. Therefore,the genotype of person Ⅲ2 must be different from the genotype of person Ⅲ7.C. True.D. False. Pedigree 5 shows that the disorder was caused by a recessive allele on X-chromosome. In the pedigree 4, the male Ⅳ3 is affected therefore females Ⅲ3, Ⅱ2 and Ⅰ1 must be carriers. Chance of the recessive alleles be passed on from female I, to female Ⅱ4 is 1/2, from female Ⅱ4 to female Ⅲ7 is 1/2, from female Ⅲ7 to female Ⅳ4 is 1/2 and from female Ⅳ4 to her son is 1/2. Therefore we can calculate the probability for the son to be affected is 1/2 * 1/2 * 1/2 = 0.0625.