A woman is married for the second time. Her first husband was ABO blood type A, and her child by that marriage was type O. Her new husband is type B and their child is type AB. What is the woman's ABO genotype and blood type

Options

A. `I^(A)I^(O)` Blood type A
B. `I^(A)I^(B)` Blood type AB
C. `I^(B)I^(O)` Blood type of B
D. `I^(O)I^(O)` Blood type O

Answer

To determine the woman's ABO genotype and blood type, we can follow these steps:

### Step 1: Analyze the first marriage
- The first husband has blood type A. His genotype can be either IAIA (homozygous A) or IAIO (heterozygous A).
- The child from the first marriage has blood type O, which means the child must have the genotype ii (IOIO).

### Step 2: Determine the woman's genotype from the first marriage
- Since the child is type O (ii), and one allele (IO) must come from the father (the first husband), the mother must also provide an IO allele.
- Therefore, the woman must have the genotype IAIO (heterozygous A).

### Step 3: Analyze the second marriage
- The new husband has blood type B. His genotype can be either IBIB (homozygous B) or IBIO (heterozygous B).
- The child from the second marriage has blood type AB, which means the child has the genotype IAIB.

### Step 4: Determine the woman's contribution in the second marriage
- For the child to have blood type AB (IAIB), one allele (IA) must come from the mother (the woman) and the other allele (IB) must come from the father (the new husband).
- Since we already established that the woman’s genotype is IAIO, she can provide the IA allele.

### Step 5: Conclusion
- The woman's genotype is IAIO, which corresponds to blood type A.

### Final Answer
The woman's ABO genotype is IAIO, and her blood type is A.

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