1 : 1 : 1 :1 ratio shows

Options

A. Monohybrid cross
B. Dihybrid cross
C. Back cross
D. Dihybrid test cross

Answer

To solve the question regarding the 1:1:1:1 ratio, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Ratios**: The ratio of 1:1:1:1 indicates that there are four distinct phenotypes or genotypes being produced in equal proportions.

2. **Identify the Context**: This ratio is typically observed in genetic crosses. We need to determine which type of genetic cross produces this specific ratio.

3. **Consider the Types of Crosses**:
- **Monohybrid Cross**: This involves a single trait and typically results in a 3:1 or 1:2:1 ratio.
- **Dihybrid Cross**: This involves two traits and typically results in a 9:3:3:1 ratio.
- **Backcross**: This is a cross between a hybrid and one of its parents, which does not necessarily produce a 1:1:1:1 ratio.
- **Dihybrid Test Cross**: This involves crossing a dihybrid individual with a homozygous recessive individual for both traits.

4. **Analyze the Dihybrid Test Cross**: In a dihybrid test cross, if we take an individual that is heterozygous for two traits (e.g., YyRr) and cross it with a homozygous recessive individual (yyrr), the gametes produced will combine to yield four different phenotypes in a 1:1:1:1 ratio.

5. **Conclusion**: Based on the analysis, the 1:1:1:1 ratio is characteristic of a dihybrid test cross.

### Final Answer:
The answer to the question is **D) Dihybrid Test Cross**.

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