[A]: The sex linked genes are passed on to the grandson through the daughter.
[R]: The Y chromosome of the grandson is received from the maternal grandfather

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

To analyze the given statements regarding sex-linked genes and inheritance, we will break down the assertion and reason step by step.

### Step-by-Step Solution:

1. **Understanding Sex-Linked Genes**:
- Sex-linked genes are located on the sex chromosomes, primarily the X and Y chromosomes. In humans, color blindness is a common example of a sex-linked recessive trait.

2. **Assertion Analysis**:
- The assertion states that "The sex-linked genes are passed on to the grandson through the daughter."
- This is true because a daughter can inherit the sex-linked gene from her father (who may be affected) and pass it on to her son (the grandson).

3. **Reason Analysis**:
- The reason states that "The Y chromosome of the grandson is received from the maternal grandfather."
- This is false because the grandson receives his Y chromosome from his father, not from his maternal grandfather. The maternal grandfather contributes to the X chromosome that the daughter carries.

4. **Conclusion**:
- The assertion is true, while the reason is false. Therefore, the correct answer is that the assertion is true, but the reason is false.

### Final Answer:
- Assertion [A] is true.
- Reason [R] is false.
- The correct option is that the assertion is true, but the reason is false.

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