Given below are assertion and reason. Point our if both are true with reason being correct explanation (A), both are true but reason is not correct explanation (B), assertion is true but reason is wrong ( C) and both are wrong (D).
Assertion. A genetist crossed two plants. He got 50% tall and 50% dwarf plants in the progeny
Reason. One parent was heterozygous tall while the other was dwarf

Options

A. A
B. B
C. C
D. D

Answer

To solve the given question, we will analyze both the assertion and the reason step by step.

### Step 1: Analyze the Assertion
The assertion states: "A geneticist crossed two plants. He got 50% tall and 50% dwarf plants in the progeny."
- This indicates a phenotypic ratio of 1:1, which is typical in a monohybrid cross involving a heterozygous tall plant and a homozygous dwarf plant.

### Step 2: Analyze the Reason
The reason states: "One parent was heterozygous tall while the other was dwarf."
- A heterozygous tall plant can be represented as Tt (where T = tall allele and t = dwarf allele) and the dwarf plant as tt (homozygous dwarf).
- When we perform the cross Tt (heterozygous tall) x tt (homozygous dwarf), we can determine the possible offspring.

### Step 3: Perform the Cross
1. **Gametes**:
- The gametes from the heterozygous tall parent (Tt) are T and t.
- The gametes from the dwarf parent (tt) are t and t.

2. **Punnett Square**:
- When we set up the Punnett square:
```
T t
-----------
t | Tt | tt |
-----------
t | Tt | tt |
```
- The offspring will be:
- 50% Tt (tall)
- 50% tt (dwarf)

### Step 4: Conclusion
- The assertion is true because the cross results in 50% tall and 50% dwarf plants.
- The reason is also true and correctly explains the assertion, as the heterozygous tall parent crossed with a homozygous dwarf parent leads to the observed ratio.

### Final Answer
Both the assertion and reason are true, and the reason is the correct explanation of the assertion. Therefore, the correct option is **A**.

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