A tall true breeding garden pea plant is crossed with a dwarf true breeding garden pea plant. Whan the `F_(1)` plants were selfed the resulting genotypes were in the ratio of :

Options

A. 1 : 2: 1 : : Tall homozygous: Tall heterozygous : Dwarf
B. 1 : 2 : 1 : : Tall heterozygous : Tall homozygous : Dwarf
C. 3 : 1 : : Tall : Dwarf
D. 3 : 1 : : Dwarf : Tall

Answer

To solve the problem of determining the genotype ratio of the offspring when a tall true-breeding garden pea plant is crossed with a dwarf true-breeding garden pea plant, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Parent Genotypes**:
- The tall true-breeding plant has the genotype **TT** (homozygous dominant).
- The dwarf true-breeding plant has the genotype **tt** (homozygous recessive).

2. **Perform the Cross**:
- When we cross these two plants (TT x tt), all offspring in the F1 generation will inherit one allele from each parent.
- Thus, the F1 generation will all have the genotype **Tt** (heterozygous).

3. **Selfing the F1 Generation**:
- When the F1 plants (Tt) are selfed (Tt x Tt), we can use a Punnett square to determine the possible genotypes of the offspring.

4. **Construct the Punnett Square**:
- The Punnett square will look like this:
```
T t
__________
T | TT | Tt |
|______|____|
t | Tt | tt |
|______|____|
```
- From the Punnett square, we can see the possible genotypes:
- **TT** (homozygous tall)
- **Tt** (heterozygous tall)
- **tt** (homozygous dwarf)

5. **Count the Genotypes**:
- From the Punnett square, we can count the genotypes:
- 1 TT
- 2 Tt
- 1 tt

6. **Determine the Genotype Ratio**:
- The genotype ratio of the offspring is **1 TT : 2 Tt : 1 tt**.

### Final Answer:
The resulting genotypes of the offspring when the F1 plants are selfed are in the ratio of **1 : 2 : 1**.

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