Trihybrid ratio is

Options

A. `27:9:9:9:3:3:3:1`
B. `27:9:9:6:6:3:3:1`
C. `1:6:15:20:15:6:1`
D. `36:6:6:6:3:3:3:1`

Answer

To find the trihybrid ratio, we need to determine both the phenotypic and genotypic ratios for a trihybrid cross. Here’s a step-by-step solution:

### Step 1: Understand the Concept of Trihybrid Cross
A trihybrid cross involves three pairs of contrasting traits. When we perform a cross involving three traits, we denote the number of heterozygous loci (n) as 3.

### Step 2: Use the Formulas for Ratios
- **Phenotypic Ratio Formula**: The formula for the phenotypic ratio in a trihybrid cross is \(3:1\) raised to the power of \(n\).
- **Genotypic Ratio Formula**: The formula for the genotypic ratio in a trihybrid cross is \(1:2:1\) raised to the power of \(n\).

### Step 3: Calculate the Phenotypic Ratio
For a trihybrid cross (n = 3):
- Phenotypic ratio = \( (3:1)^3 \)
- This expands to \( 27:9:9:9:3:3:3:1 \)

### Step 4: Calculate the Genotypic Ratio
For a trihybrid cross (n = 3):
- Genotypic ratio = \( (1:2:1)^3 \)
- This expands to \( 1:2:1, 1:2:1, 1:2:1 \) which results in \( 1:2:1:2:4:2:1:2:1 \)

### Step 5: Final Ratios
- **Phenotypic Ratio**: \( 27:9:9:9:3:3:3:1 \)
- **Genotypic Ratio**: \( 1:2:1:2:4:2:1:2:1 \)

### Conclusion
The trihybrid ratio can be summarized as:
- **Phenotypic Ratio**: \( 27:9:9:9:3:3:3:1 \)
- **Genotypic Ratio**: \( 1:2:1:2:4:2:1:2:1 \)