To determine the phenotypes of the parents, you need to understand how blood type and Rh factors are inherited. Let's break it down step by step:
a. Phenotypes of the parents:
- The father has the genotype IA IO Rh+ Rh–. Based on the genotype, we can determine the blood group and the Rh factor separately:
- The ABO blood group genotype IA IO indicates that the father has blood group A (genotype IA) and carries the genetic variant for blood group O (genotype IO).
- The Rh genotype of Rh+ Rh– indicates that the father is positive for the Rh factor.
Therefore, the father's phenotype is A-positive (blood group A and Rh+).
- The mother has the genotype IA IB Rh+ Rh–. In a similar manner, we can determine her blood group and Rh factor:
- The ABO blood group genotype IA IB indicates that the mother has blood group AB, as she has the genetic variants for both blood groups A (genotype IA) and B (genotype IB).
- The Rh genotype of Rh+ Rh– tells us that the mother is positive for the Rh factor.
Thus, the mother's phenotype is AB-positive (blood group AB and Rh+).
b. To determine the probability of their only child having the phenotype B-positive, we need to understand how the genotypes can be combined during inheritance.
The possibilities for the child's blood type can be determined by combining the ABO genotypes of the parents: IA and IB.
The possible genotypes for the child are:
- IA IA (blood group A)
- IA IB (blood group AB)
- IA IO (blood group A)
- IB IB (blood group B)
- IB IO (blood group B)
- IO IO (blood group O)
Since the Rh factor is dominant, if either parent carries the Rh+ allele, the child will be Rh-positive.
Out of the six possible genotypes, only the genotype IB IB will result in a B-positive blood type.
Therefore, the probability that their only child will have the phenotype B-positive is 1 out of 6, or approximately 16.67%.