A child of O blood group was born to a mother of blood group A and father of blood group B. What are the genotypes of parents?

Options

A. mother-I_(A),I_(A)`., father-`I_(B)I_(B)`
B. mother-`I_(A)I_(O)`, father-`I_(B)I_(O)`
C. mother-`I_(B)I_(B),` father-`I_(A)I_(A)`
D. mother - `I_(B)I_(O)`, father- `I_(A)I_(O)`

Answer

To determine the genotypes of the parents based on the blood group of the child, we can follow these steps:

### Step 1: Understand Blood Group Genetics
Blood groups are determined by the presence of specific alleles. The main alleles are:
- I^A (A blood group)
- I^B (B blood group)
- i (O blood group)

### Step 2: Identify the Child's Blood Group
The child has blood group O. The genotype for blood group O is homozygous recessive, which is represented as "ii".

### Step 3: Analyze the Parents' Blood Groups
The mother has blood group A, which can have the following genotypes:
- Homozygous: I^A I^A
- Heterozygous: I^A i

The father has blood group B, which can have the following genotypes:
- Homozygous: I^B I^B
- Heterozygous: I^B i

### Step 4: Determine Possible Combinations
To have a child with blood group O (genotype ii), at least one parent must contribute an "i" allele. Therefore, we need to consider the heterozygous conditions for both parents.

- If the mother is heterozygous (I^A i) and the father is heterozygous (I^B i), the possible combinations from their offspring would be:
- I^A I^B (AB blood group)
- I^A i (A blood group)
- I^B i (B blood group)
- ii (O blood group)

### Step 5: Conclude the Genotypes
Since the child has blood group O, the only possible genotypes for the parents that would allow for this outcome are:
- Mother: I^A i (heterozygous A)
- Father: I^B i (heterozygous B)

### Final Answer
The genotypes of the parents are:
- Mother: I^A i
- Father: I^B i

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