Assertion: A geneticist crossed a pea plant having violet flowers with a pea plant with white flowers, he got all violet flowers in first generation.
Reason: White colour gene is not passed on to next generation.

Options

A. Both A and R are true, and R is correct explanation of the assertion.
B. Both A and R are true, but R is not the correct explanation of the assertion.
C. A is true, but R is false.
D. A is false, but R is true.

Explanation

To solve the question, we need to analyze the assertion and reason provided:

**Assertion:** A geneticist crossed a pea plant having violet flowers with a pea plant with white flowers, and he got all violet flowers in the first generation.

**Reason:** The white color gene is not passed on to the next generation.

### Step-by-Step Solution:

1. **Identify the Traits:**
- The violet flower color is a dominant trait, while the white flower color is a recessive trait.
- We can represent the violet flower gene with a capital letter (W) and the white flower gene with a lowercase letter (w).

2. **Parental Generation (P1 and P2):**
- Let's denote the pea plant with violet flowers as P1 (WW) and the pea plant with white flowers as P2 (ww).
- Here, P1 is homozygous dominant (WW) and P2 is homozygous recessive (ww).

3. **Gamete Formation:**
- P1 can only produce gametes with the dominant allele (W).
- P2 can only produce gametes with the recessive allele (w).

4. **F1 Generation:**
- When we cross P1 and P2, the gametes combine:
- All offspring (F1 generation) will have the genotype Ww (one dominant allele from P1 and one recessive allele from P2).
- The phenotype of all F1 plants will be violet flowers because the dominant trait (W) masks the recessive trait (w).

5. **Evaluate the Assertion:**
- The assertion is true: crossing a violet flower plant with a white flower plant results in all violet flowers in the first generation.

6. **Evaluate the Reason:**
- The reason states that the white color gene is not passed on to the next generation. This is misleading because the white color gene (w) is indeed present in the F1 generation (as Ww), but it is not expressed due to the dominance of the violet color gene (W).
- Therefore, the reason is false.

7. **Conclusion:**
- The assertion is true, but the reason is false. Thus, the correct answer is option C: "Assertion is true but reason is false."