Dominant gene for tallness is T and for yellow color is Y. A plant heterozygous for both the traits is selfed, then the ratio of pure homozygous dwarf and green offspring would be

Options

A. `1//4`
B. `4//16`
C. `3//16`
D. `1//16`

Answer

To solve the problem, we need to analyze the genetic cross of a plant that is heterozygous for both traits: tallness (T) and color (Y). The dominant gene for tallness is T (tall) and the recessive gene is t (dwarf). The dominant gene for color is Y (yellow) and the recessive gene is y (green).

### Step-by-Step Solution:

1. **Identify the Genotype of the Parent Plant**:
- The plant is heterozygous for both traits, so its genotype will be TtYy.

2. **Set Up the Dihybrid Cross**:
- When we self the plant (TtYy x TtYy), we need to set up a Punnett square for a dihybrid cross.

3. **Determine the Gametes**:
- The possible gametes from the TtYy parent are: TY, Ty, tY, and ty.

4. **Create the Punnett Square**:
- Set up a 4x4 Punnett square using the gametes:
```
TY Ty tY ty
---------------------------
TY | TTYY | TTYy | TtYY | TtYy |
---------------------------
Ty | TTYy | TTyy | TtYy | Ttyy |
---------------------------
tY | TtYY | TtYy | ttYY | ttYy |
---------------------------
ty | TtYy | Ttyy | ttYy | ttyy |
---------------------------
```

5. **Count the Offspring Phenotypes**:
- From the Punnett square, we can categorize the phenotypes:
- Tall and Yellow (T_Y): 9 (TTYY, TTYy, TtYY, TtYy)
- Tall and Green (T_yy): 3 (TTyy, Ttyy)
- Dwarf and Yellow (ttY_): 3 (ttYY, ttYy)
- Dwarf and Green (ttyy): 1 (ttyy)

6. **Identify the Pure Homozygous Dwarf and Green Offspring**:
- The only genotype that corresponds to dwarf and green is ttyy.
- According to the Punnett square, there is 1 ttyy out of 16 total offspring.

7. **Calculate the Ratio**:
- The ratio of pure homozygous dwarf (ttyy) and green offspring is 1 out of 16.

### Final Answer:
The ratio of pure homozygous dwarf and green offspring is **1:16**.

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