A : The hetrozygotic female for haemophilia may transmit the disease to sons.
R : Such traits show criss-cross inheritance.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1)
B. If both Assertion & Reason are true and the reason is not the correct explanation of the assertion , then mark (2)
C. If Assertion is true statement but Reason is false, then mark (3)
D. If both Assertion and Reason are false statements, then mark (4)

Answer

To solve the assertion and reason question regarding hemophilia and criss-cross inheritance, we can break it down into the following steps:

### Step 1: Understand the Assertion
The assertion states that a heterozygotic female for hemophilia may transmit the disease to her sons.

- **Explanation**: Hemophilia is a sex-linked recessive disorder caused by a defective gene located on the X chromosome. A heterozygotic female (XHXh) has one normal allele (XH) and one defective allele (Xh). When she has sons, they inherit one X chromosome from her and one Y chromosome from their father.

### Step 2: Understand the Reason
The reason states that such traits show criss-cross inheritance.

- **Explanation**: Criss-cross inheritance refers to the pattern where a trait is passed from a mother to her son and then from that son to his daughter. In this case, the mother (heterozygotic female) can pass the defective X chromosome (Xh) to her son, making him hemophiliac (XhY). If this son has children, he can pass the Y chromosome to his sons and the Xh chromosome to his daughters, leading to the daughters potentially being carriers of hemophilia.

### Step 3: Analyze the Relationship Between Assertion and Reason
Now we need to determine if the reason correctly explains the assertion.

- **Explanation**: The assertion is true because a heterozygotic female can indeed transmit hemophilia to her sons. The reason is also true, as criss-cross inheritance accurately describes the pattern of inheritance for sex-linked traits like hemophilia. The reason provides a correct explanation for the assertion.

### Step 4: Conclusion
Based on the analysis, both the assertion and the reason are true, and the reason is the correct explanation for the assertion.

- **Final Answer**: Option 1: Both assertion and reason are true, and the reason is the correct explanation of the assertion.

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