A homozygous tall pea plant with yellow pods is crossed with a homozygous dwarf pea plant with the green pods. The off springs produced are salted. In the `F_2` generation , the ratio of plants having parental combinations to new combinations is

Options

A. `10:6`
B. `6:10`
C. `9:7`
D. `7:9`

Answer

To solve the problem, we will follow these steps:

### Step 1: Identify the Genotypes of the Parents
- The first parent is a homozygous tall pea plant with yellow pods. Since tall (T) is dominant over dwarf (t) and yellow (G) is dominant over green (g), the genotype of this parent is **TTGG**.
- The second parent is a homozygous dwarf pea plant with green pods, which has the genotype **ttgg**.

### Step 2: Determine the Gametes from Each Parent
- The gametes produced by the first parent (TTGG) will be **TG**.
- The gametes produced by the second parent (ttgg) will be **tg**.

### Step 3: Cross the Parents to Get the F1 Generation
- When we cross these two parents, all offspring in the F1 generation will be heterozygous for both traits: **TtGg**.

### Step 4: Self-Pollinate the F1 Generation to Produce the F2 Generation
- The F1 generation (TtGg) will self-pollinate. The possible gametes produced by F1 plants are:
- **TG**
- **Tg**
- **tG**
- **tg**

### Step 5: Create a Punnett Square for the F2 Generation
- Set up a Punnett square with the gametes from two F1 plants:
```
TG Tg tG tg
-------------------------
TG | TTGG TTGg TtGG TtGg
-------------------------
Tg | TTGg TTgg TtGg Ttgg
-------------------------
tG | TtGG TtGg ttGG ttGg
-------------------------
tg | TtGg Ttgg ttGg ttgg
```

### Step 6: Count the Offspring Phenotypes
- From the Punnett square, we can identify the phenotypes:
- **Tall Yellow Pods (TTGG, TTGg, TtGG, TtGg)**: 9
- **Tall Green Pods (Ttgg, ttGg)**: 3
- **Dwarf Yellow Pods (TTgg, TtGg)**: 3
- **Dwarf Green Pods (ttgg)**: 1

### Step 7: Identify Parental and New Combinations
- Parental combinations:
- Tall Yellow (TTGG, TTGg)
- Dwarf Green (ttgg)
- New combinations:
- Tall Green (TtGg)
- Dwarf Yellow (Ttgg)

### Step 8: Calculate the Ratio of Parental to New Combinations
- Total parental combinations = 6 (TTGG, TTGg, ttgg)
- Total new combinations = 10 (TtGg, Ttgg)
- The ratio of plants having parental combinations to new combinations is **6:10**, which simplifies to **3:5**.

### Final Answer
The ratio of plants having parental combinations to new combinations in the F2 generation is **3:5**.

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