A : Test cross is the tool for knowing linkage between genes.
R : Monohybrid test cross gives two phenotypes and two genotypes.

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 analyze the given statements regarding test crosses and monohybrid test crosses, let's break it down step by step.

### Step 1: Understand the Assertion
The assertion states that "test cross is the tool for knowing linkage between genes."

- **Explanation**: A test cross involves crossing an individual with an unknown genotype (usually heterozygous) with a homozygous recessive individual. This method helps determine whether the genes are linked or not based on the phenotypic ratios of the offspring.

### Step 2: Validate the Assertion
Is the assertion true?
- **Conclusion**: Yes, the assertion is true. Test crosses are indeed used to determine the linkage between genes.

### Step 3: Understand the Reason
The reason states that "monohybrid test cross gives two phenotypes and two genotypes."

- **Explanation**: In a monohybrid test cross, you typically cross a heterozygous individual (e.g., Tt) with a homozygous recessive individual (tt). The offspring can exhibit two phenotypes (tall and dwarf) and two genotypes (TT, Tt, and tt).

### Step 4: Validate the Reason
Is the reason true?
- **Conclusion**: Yes, the reason is also true. A monohybrid test cross results in two distinct phenotypes and two genotypes.

### Step 5: Determine the Relationship Between Assertion and Reason
- The assertion is true, and the reason is true, but does the reason explain the assertion?
- **Conclusion**: The reason does not explain the assertion. While both statements are true, the reason does not provide a direct explanation for the assertion regarding the linkage of genes.

### Final Conclusion
Both the assertion and reason are true, but the reason does not serve as a correct explanation for the assertion. Therefore, the correct option is that both are true, but the reason is not a correct explanation of the assertion.

---