In dihybrid cross,the test cross ratio will be

Options

A. 9:3:3:1
B. 1:1:1:1
C. `1:1`
D. `15:1`

Answer

To solve the question regarding the test cross ratio in a dihybrid cross, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Dihybrid Cross**:
- A dihybrid cross involves two traits, each represented by two alleles. For example, we can consider traits for seed color (yellow - Y, green - y) and seed shape (round - R, wrinkled - r).

2. **Identifying the Parental Genotypes**:
- In this case, we have a hybrid organism with dominant traits (Y and R) crossed with an organism that has recessive traits (y and r).
- The genotypes are:
- Hybrid: YR (Yellow Round)
- Recessive: yyrr (Green Wrinkled)

3. **Setting Up the Test Cross**:
- The test cross is performed by crossing the hybrid (YR) with the double recessive (yyrr).
- The gametes from the hybrid (YR) can produce two types of gametes: YR and yr.

4. **Gamete Formation**:
- The gametes from the hybrid parent (YR) will combine with the gametes from the recessive parent (yyrr):
- YR x yyrr → Possible combinations:
- YR (from hybrid) with yy (from recessive) → Yellow Round (YyRr)
- Yr (from hybrid) with yy (from recessive) → Yellow Wrinkled (Yyrr)
- yR (from hybrid) with yy (from recessive) → Green Round (yyRr)
- yr (from hybrid) with yy (from recessive) → Green Wrinkled (yyrr)

5. **Counting the Progeny**:
- The resulting progeny from the test cross will be:
- 1 Yellow Round (YyRr)
- 1 Yellow Wrinkled (Yyrr)
- 1 Green Round (yyRr)
- 1 Green Wrinkled (yyrr)

6. **Calculating the Ratio**:
- The phenotypic ratio of the progeny is:
- Yellow Round : Yellow Wrinkled : Green Round : Green Wrinkled = 1 : 1 : 1 : 1

7. **Conclusion**:
- Therefore, the test cross ratio in a dihybrid cross is **1:1:1:1**.

### Final Answer:
The test cross ratio in a dihybrid cross is **1:1:1:1**.

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