Which of the following combination of parents can produce a child with erythroblastosis fetalis?

Options

A. Rh-ve Mother and Rh+ve Father
B. Rh+ve Mother and Rh-ve Father
C. Rh+ve Mother and Rh+ Father
D. Rh-ve Mother and Rh-ve Father

Answer

To solve the question regarding which combination of parents can produce a child with erythroblastosis fetalis, we need to understand the genetic basis of this condition.

### Step-by-Step Solution:

1. **Understanding Erythroblastosis Fetalis**:
- Erythroblastosis fetalis is a condition that occurs when there is an incompatibility between the blood types of the mother and the fetus, specifically concerning the Rh factor.
- The Rh factor is determined by the presence or absence of the Rh antigen (D antigen) on red blood cells.

2. **Rh Positive and Rh Negative**:
- Individuals with the Rh antigen are classified as Rh positive (e.g., A+, B+, O+).
- Individuals without the Rh antigen are classified as Rh negative (e.g., A-, B-, O-).
- The Rh factor is a dominant trait, meaning that if one parent is Rh positive, they can pass on the Rh positive trait to their offspring.

3. **Parental Combinations**:
- For erythroblastosis fetalis to occur, the mother must be Rh negative, and the father must be Rh positive.
- If the mother is Rh negative and the father is Rh positive, their first child may inherit the Rh positive trait from the father.
- If the mother is exposed to Rh positive blood (from the fetus), she will produce antibodies against the Rh antigen.

4. **Subsequent Pregnancies**:
- If the mother becomes pregnant again with another Rh positive fetus, her pre-existing antibodies against the Rh antigen can cross the placenta and attack the fetal red blood cells, leading to erythroblastosis fetalis.

5. **Conclusion**:
- Therefore, the combination of parents that can produce a child with erythroblastosis fetalis is when the mother is Rh negative and the father is Rh positive.

### Final Answer:
The combination of parents that can produce a child with erythroblastosis fetalis is:
- Mother: Rh negative (e.g., A-)
- Father: Rh positive (e.g., A+)

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