Ratio 1:1:1:1 is obtained from a cross of

Options

A. RRYY `xx` rryy
B. RRYy `xx` rrYy
C. RrYY `xx` Rryy
D. RrYy `xx`rryy

Answer

To solve the question regarding the 1:1:1:1 ratio obtained from a genetic cross, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Ratio**: The ratio 1:1:1:1 indicates that there are four different phenotypes produced in equal proportions. This typically arises from a dihybrid cross where one parent is heterozygous for two traits and the other parent is homozygous recessive for those traits.

2. **Identify the Traits**: Let's assume we are dealing with two traits:
- Trait 1: Round (R) vs. Wrinkled (r) seeds
- Trait 2: Yellow (Y) vs. Green (y) seeds

3. **Determine Parental Genotypes**: For the 1:1:1:1 ratio, we can use the following parental genotypes:
- Parent 1 (heterozygous for both traits): RrYy
- Parent 2 (homozygous recessive for both traits): rryy

4. **Gamete Formation**:
- The heterozygous parent (RrYy) can produce four types of gametes: RY, Ry, rY, and ry.
- The homozygous recessive parent (rryy) can only produce one type of gamete: ry.

5. **Set Up a Punnett Square**: Create a Punnett square to visualize the cross:
- The gametes from RrYy (RY, Ry, rY, ry) are placed on one side, and the gamete from rryy (ry) is placed on the other side.

6. **Fill in the Punnett Square**:
- RY x ry = RrYy (Round Yellow)
- Ry x ry = Rryy (Round Green)
- rY x ry = rrYy (Wrinkled Yellow)
- ry x ry = rryy (Wrinkled Green)

7. **Count the Phenotypes**: The resulting offspring from the cross will show:
- 1 Round Yellow (RrYy)
- 1 Round Green (Rryy)
- 1 Wrinkled Yellow (rrYy)
- 1 Wrinkled Green (rryy)

8. **Conclusion**: The phenotypic ratio of the offspring is 1:1:1:1, confirming that the cross of RrYy (heterozygous) with rryy (homozygous recessive) produces this ratio.

### Final Answer:
The ratio 1:1:1:1 is obtained from a cross of RrYy (heterozygous) and rryy (homozygous recessive).

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