[A]: Genetic disorder, sickle cell anaemia is common in new born babies·
[R]: It is caused by heterozygosity for allble Hbc, producing a single ammo acid substitu tion in the a-chain of the Haemoglobin deter- mined by allele `Hb^A`

Options

A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that sickle cell anemia is a genetic disorder that is common in newborn babies. This is true, as sickle cell anemia is indeed a genetic disorder that can be inherited from parents to their children.

2. **Understanding the Reasoning**:
- The reasoning provided suggests that sickle cell anemia is caused by heterozygosity for the allele Hb^c, which leads to a single amino acid substitution in the alpha chain of hemoglobin determined by the allele Hb^A. This statement is misleading.
- Sickle cell anemia is primarily caused by a mutation in the beta chain of hemoglobin, specifically a substitution of glutamic acid with valine due to the presence of the Hb^S allele.

3. **Identifying the Correctness of the Statements**:
- The assertion is correct: Sickle cell anemia is common in newborns.
- The reasoning is incorrect: It misrepresents the genetic basis of sickle cell anemia by incorrectly attributing it to heterozygosity and an incorrect substitution in the alpha chain.

4. **Conclusion**:
- Since the assertion is true and the reasoning is false, the relationship between them is that one is correct while the other is not. Therefore, the correct answer is that the assertion is true, but the reasoning is false.

### Final Answer:
- The assertion is true, and the reasoning is false.

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