[A]: Each gemete has only one allele for each trait.
[R]: It is true of single trait crosses only.

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 solve the assertion and reasoning question, let's break it down step by step.

### Step 1: Understand the Assertion
The assertion states: "Each gamete has only one allele for each trait."

- **Explanation**: This statement is true. Gametes are haploid cells, meaning they contain only one set of chromosomes. Therefore, for each trait, a gamete will carry only one allele. This is consistent with Mendel's law of segregation, which states that during gamete formation, the alleles for a trait separate so that each gamete receives only one allele.

### Step 2: Understand the Reasoning
The reasoning states: "It is true of single trait crosses only."

- **Explanation**: This statement is false. While it is true that each gamete carries only one allele for each trait, this principle applies not only to single trait crosses (monohybrid crosses) but also to multiple trait crosses (dihybrid crosses and beyond). In dihybrid crosses, for example, each gamete still carries only one allele for each trait, even though multiple traits are being considered.

### Step 3: Conclusion
Based on the analysis:
- Assertion (A) is true.
- Reasoning (R) is false.

Thus, the correct answer is that the assertion is true, but the reasoning is false.

### Final Answer
- **Assertion (A)**: True
- **Reasoning (R)**: False
- Therefore, the answer is C: A is true, R is false.

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