Final answer:
Tom's genotype must be BO, as he has type B blood and his daughter with Tanya, who has type O blood, also has type O blood. Since type O blood is recessive, Tom must carry the O allele to have a child with type O blood, indicating his genotype is BO and the daughter inherited an i allele from each parent.
Step-by-step explanation:
Blood Type Inheritance
The question poses a scenario where Tom has type B blood and his daughter with Tanya, who has type O blood, also has type O blood. In order for the daughter to have type O blood, Tom must carry the O allele. Since he has type B blood, his genotype must be BO. This means his blood type could still be B, but he carries the recessive O allele. Hence, Tom's possible genotypes are BO or BB. However, since the daughter has type O blood, Tom's genotype can only be BO.
Given that individuals with type O blood have a genotype of ii, meaning they have inherited an i allele from each parent, the daughter in this scenario must have inherited an i allele from each parent. Tanya has type O blood (genotype ii), so she contributes an i allele. Since the daughter's other allele must also be i (resulting in ii genotype), Tom must have contributed the other i allele, and therefore, his genotype must include the i allele.
When looking at ABO blood group inheritance, as illustrated in Figure 17.6.4, a male with type A (genotype AO) and a female with type B (genotype BO) can have offspring with each of the four possible phenotypes (A, AB, B, and O), demonstrating that the presence of the O phenotype in offspring indicates that both parents must carry the O allele.