Each person can have one of four possible blood types: A, B, AB, or O....
Each person can have one of four possible blood types: A, B, AB, or O. Blood type A means that the A antigen is present on the red blood cell surface. Blood type B means that the B antigen is present on red blood cells' surfaces. Blood type AB means that both the A antigen and the B antigen are present on the red blood cells' surfaces. Blood type O means that no antigens are present on the red blood cells' surfaces. Someone with genotype A/A or A/O will have type A blood. Someone with genotype B/B or B/O will have type B blood. Someone with genotype A/B will have AB blood, and someone with genotype O/O will have type O blood. Assuming that blood type is not a sex-linked trait, what is the probability that a mother with genotype A/O and a father with genotype A/B will have a child with type B blood?
- A. 1.0
- B. 0.25
- C. 0.75
- D. 0.50
Correct Answer: B. 0.25
Explanation
The easiest way to solve this problem is to draw a punnet square. The genotypes of the parents are AO and AB. The potential genotypes of their children are AA, AO, BA, and BO. Only genotype BO will produce type B blood. BO is one out of four results of this punnet square, so the probability of this outcome is 1/4=0.25.